Error when cosigning transaction: SSLCertVerificationError

Hello, let me just clarify that I am not a developer, however I am an advanced user of electrum/bitcoin and have some good general knowledge about coding.

Me and my cosigner both have created a new fresh seed in electrum just to test the multisig functionality, the idea is to use 2 hardware wallets located in different areas once we make sure everything works as expected.
I have an issue with my electrum when trying to send a transaction to my cosigner.
I want to send it through the cosigning pool (plugin enabled on both clients).
I get this error:
Failed to send transaction to cosigning pool:
SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: self signed certificate in certificate chain (_ssl.c:1125)')

I have tried to update/reinstall electrum (I have version 4.1.5 on both cosigning windows desktops).
My OS has also the latest update.
Below you can see the logs.
Is anyone able to help me? I have tried to find the solution everywhere online (and also here) but am not able to solve this.
Let me know if you have any questions. Many thanks in advance.

20210903T091700.149517Z | INFO | simple_config.SimpleConfig | electrum directory C:\Users\myuser\AppData\Roaming\Electrum
20210903T091700.152508Z | INFO | logging | Electrum version: 4.1.5 - https://electrum.org - https://github.com/spesmilo/electrum
20210903T091700.153511Z | INFO | logging | Python version: 3.8.8 (tags/v3.8.8:024d805, Feb 19 2021, 13:08:11) [MSC v.1928 32 bit (Intel)]. On platform: Windows-10-10.0.19041-SP0
20210903T091700.153511Z | INFO | logging | Logging to file: C:\Users\myuser\AppData\Roaming\Electrum\logs\electrum_log_20210903T091700Z_13204.log
20210903T091700.153511Z | INFO | logging | Log filters: verbosity '', verbosity_shortcuts ''
20210903T091700.156474Z | INFO | plugin.Plugins | registering hardware bitbox02: ('hardware', 'bitbox02', 'BitBox02')
20210903T091700.157471Z | INFO | plugin.Plugins | registering hardware coldcard: ('hardware', 'coldcard', 'Coldcard Wallet')
20210903T091700.210776Z | INFO | gui.qt.history_list | could not import electrum.plot. This feature needs matplotlib to be installed.
20210903T091700.225735Z | INFO | plugin.Plugins | loaded cosigner_pool
20210903T091700.227698Z | INFO | plugin.Plugins | registering hardware digitalbitbox: ('hardware', 'digitalbitbox', 'Digital Bitbox wallet')
20210903T091700.229721Z | INFO | plugin.Plugins | registering hardware keepkey: ('hardware', 'keepkey', 'KeepKey wallet')
20210903T091700.230718Z | INFO | plugin.Plugins | registering hardware ledger: ('hardware', 'ledger', 'Ledger wallet')
20210903T091700.232714Z | INFO | plugin.Plugins | registering hardware safe_t: ('hardware', 'safe_t', 'Safe-T mini wallet')
20210903T091700.233710Z | INFO | plugin.Plugins | registering hardware trezor: ('hardware', 'trezor', 'Trezor wallet')
20210903T091700.234706Z | INFO | plugin.Plugins | registering wallet type ('2fa', 'trustedcoin')
20210903T091700.236377Z | DEBUG | util.profiler | Plugins.init 0.0819
20210903T091700.237258Z | INFO | network | blockchains [0]
20210903T091700.238258Z | INFO | exchange_rate.FxThread | using exchange CoinGecko
20210903T091700.239254Z | DEBUG | util.profiler | Daemon.init 0.0029
20210903T091700.239254Z | INFO | daemon.Daemon | launching GUI: qt
20210903T091700.239254Z | INFO | network | starting network
20210903T091700.241250Z | INFO | gui.qt.ElectrumGui | Qt GUI starting up... Qt=5.15.2, PyQt=5.15.4
20210903T091700.241250Z | INFO | network | setting proxy None
20210903T091700.241250Z | INFO | daemon.Daemon | starting taskgroup.
20210903T091700.242246Z | INFO | network | connecting to skbxmit.coinjoined.com:50002:s as new interface
20210903T091700.242246Z | INFO | network | starting taskgroup.
20210903T091700.370723Z | DEBUG | util.profiler | ElectrumGui.init 0.1315
20210903T091700.373742Z | INFO | interface.[skbxmit.coinjoined.com:50002] | connection established. version: ['ElectrumX 1.15.0', '1.4']
20210903T091700.373742Z | INFO | storage.WalletStorage | wallet path c:\users\myuser\appdata\roaming\electrum\wallets\wallet_test_multisig
20210903T091700.721351Z | INFO | interface.[skbxmit.coinjoined.com:50002] | set blockchain with height 698812
20210903T091700.722350Z | INFO | interface.[skbxmit.coinjoined.com:50002] | skipping header 698812
20210903T091700.722350Z | INFO | network | no height for main interface
20210903T091700.723346Z | INFO | network | switching to skbxmit.coinjoined.com:50002:s
20210903T091700.724344Z | INFO | network | fee_estimates {25: 2012, 10: 7156, 5: 10133, 2: 10718}
20210903T091700.734316Z | INFO | storage.WalletStorage | wallet path c:\users\myuser\appdata\roaming\electrum\wallets\wallet_test_multisig
20210903T091700.794801Z | INFO | network | fee_histogram [[10, 120902]]
20210903T091700.820387Z | INFO | interface.[e.keff.org:50002] | connection established. version: ['ElectrumX 1.10.0', '1.4']
20210903T091700.989770Z | INFO | interface.[e.keff.org:50002] | set blockchain with height 698812
20210903T091700.989770Z | INFO | interface.[e.keff.org:50002] | skipping header 698812
20210903T091700.989770Z | INFO | interface.[b.ooze.cc:50002] | connection established. version: ['ElectrumX 1.16.0', '1.4']
20210903T091700.991759Z | INFO | network | fee_estimates {25: 2012, 10: 7156, 5: 10133, 2: 10904}
20210903T091701.034383Z | INFO | interface.[b.ooze.cc:50002] | set blockchain with height 698812
20210903T091701.035404Z | INFO | interface.[b.ooze.cc:50002] | skipping header 698812
20210903T091701.079301Z | INFO | network | fee_estimates {25: 2012, 10: 7156, 5: 10133, 2: 10718}
20210903T091701.094589Z | INFO | interface.[xtrum.com:50002] | connection established. version: ['ElectrumX 1.15.0', '1.4']
20210903T091701.105478Z | INFO | interface.[electrum2.taborsky.cz:50002] | connection established. version: ['ElectrumX 1.15.0', '1.4']
20210903T091701.120177Z | INFO | interface.[xtrum.com:50002] | set blockchain with height 698812
20210903T091701.121177Z | INFO | interface.[xtrum.com:50002] | skipping header 698812
20210903T091701.125465Z | INFO | interface.[electrum2.taborsky.cz:50002] | set blockchain with height 698812
20210903T091701.126283Z | INFO | interface.[electrum2.taborsky.cz:50002] | skipping header 698812
20210903T091701.164463Z | INFO | interface.[bitcoin.lukechilds.co:50002] | connection established. version: ['ElectrumX 1.16.0', '1.4']
20210903T091701.213304Z | INFO | interface.[bitcoin.lukechilds.co:50002] | set blockchain with height 698812
20210903T091701.213304Z | INFO | interface.[bitcoin.lukechilds.co:50002] | skipping header 698812
20210903T091701.366943Z | INFO | interface.[vmd71287.contaboserver.net:50002] | connection established. version: ['ElectrumX 1.16.0', '1.4']
20210903T091701.494172Z | INFO | interface.[vmd71287.contaboserver.net:50002] | set blockchain with height 698812
20210903T091701.495173Z | INFO | interface.[vmd71287.contaboserver.net:50002] | skipping header 698812
20210903T091701.827261Z | INFO | interface.[169.0.140.101:50005] | succeeded in getting cert
20210903T091702.327405Z | INFO | interface.[bitcoin.aranguren.org:50002] | connection established. version: ['ElectrumX 1.16.0', '1.4']
20210903T091702.422255Z | INFO | interface.[169.0.140.101:50005] | connection established. version: ['ElectrumX 1.16.0', '1.4']
20210903T091702.588208Z | INFO | interface.[bitcoin.aranguren.org:50002] | set blockchain with height 698812
20210903T091702.590204Z | INFO | interface.[bitcoin.aranguren.org:50002] | skipping header 698812
20210903T091702.614133Z | INFO | interface.[169.0.140.101:50005] | set blockchain with height 698812
20210903T091702.615165Z | INFO | interface.[169.0.140.101:50005] | skipping header 698812
20210903T091704.169086Z | INFO | interface.[btc.ocf.sh:50002] | succeeded in getting cert
20210903T091705.588070Z | INFO | interface.[btc.ocf.sh:50002] | connection established. version: ['ElectrumX 1.16.0', '1.4']
20210903T091705.975111Z | INFO | interface.[btc.ocf.sh:50002] | set blockchain with height 698812
20210903T091705.976111Z | INFO | interface.[btc.ocf.sh:50002] | skipping header 698812
20210903T091743.347657Z | DEBUG | util.profiler | WalletDB._load_transactions 0.0010
20210903T091743.360018Z | DEBUG | util.profiler | AddressSynchronizer.load_local_history 0.0000
20210903T091743.361013Z | DEBUG | util.profiler | AddressSynchronizer.check_history 0.0000
20210903T091743.483924Z | DEBUG | util.profiler | AddressList.update 0.0000
20210903T091743.595861Z | INFO | plugins.cosigner_pool.qt.Plugin | starting listener
20210903T091743.654092Z | DEBUG | util.profiler | Deterministic_Wallet.try_detecting_internal_addresses_corruption 0.0482
20210903T091743.655080Z | DEBUG | util.profiler | ElectrumWindow.load_wallet 0.1246
20210903T091743.661920Z | INFO | gui.qt.ElectrumGui | starting Qt main loop
20210903T091743.892536Z | INFO | gui.qt.update_checker.UpdateCheckThread | got exception: 'ClientConnectorCertificateError(ConnectionKey(host='electrum.org', port=443, is_ssl=True, ssl=None, proxy=None, proxy_auth=None, proxy_headers_hash=-1910352697), SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: self signed certificate in certificate chain (_ssl.c:1125)'))'
20210903T091745.705332Z | INFO | plugins.cosigner_pool.qt.Listener | cannot contact cosigner pool
20210903T091746.858207Z | INFO | wallet.Multisig_Wallet.[wallet_test_multisig] | set_up_to_date: True
20210903T091746.868099Z | INFO | storage.WalletStorage | saved c:\users\myuser\appdata\roaming\electrum\wallets\wallet_test_multisig
20210903T091746.868099Z | DEBUG | util.profiler | WalletDB._write 0.0099
20210903T091746.878055Z | INFO | gui.qt.history_list.HistoryModel | refreshing... reason: update_tabs
20210903T091746.878055Z | DEBUG | util.profiler | Abstract_Wallet.get_full_history 0.0000
20210903T091746.879053Z | DEBUG | util.profiler | HistoryModel.refresh 0.0010
20210903T091746.880050Z | DEBUG | util.profiler | AddressList.update 0.0000
20210903T091801.700035Z | INFO | network | fee_histogram [[10, 120902]]
20210903T091805.329309Z | INFO | transaction | adding signature for 02074c09887afa96b209f82bbb90d6ac74ff9027518e6187fb117ff105e63b8695
20210903T091805.331322Z | DEBUG | transaction | is_complete False
20210903T091815.357703Z | ERROR | plugins.cosigner_pool.qt.Plugin | on_failure
Traceback (most recent call last):
File "electrum\gui\qt\util.py", line 914, in run
File "C:\Program Files (x86)\Electrum\electrum\plugins\cosigner_pool\qt.py", line 209, in send_messages_task
server.put(_hash, message)
File "xmlrpc\client.py", line 1109, in call
File "xmlrpc\client.py", line 1450, in __request
File "xmlrpc\client.py", line 1153, in request
File "xmlrpc\client.py", line 1165, in single_request
File "xmlrpc\client.py", line 1278, in send_request
File "xmlrpc\client.py", line 1308, in send_content
File "http\client.py", line 1250, in endheaders
File "http\client.py", line 1010, in _send_output
File "http\client.py", line 950, in send
File "http\client.py", line 1424, in connect
File "ssl.py", line 500, in wrap_socket
File "ssl.py", line 1040, in _create
File "ssl.py", line 1309, in do_handshake
ssl.SSLCertVerificationError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: self signed certificate in certificate chain (_ssl.c:1125)
20210903T091819.157556Z | INFO | gui.qt.main_window.[wallet_test_multisig] | close_wallet c:\users\myuser\appdata\roaming\electrum\wallets\wallet_test_multisig
20210903T091819.167935Z | INFO | plugins.cosigner_pool.qt.Plugin | shutting down listener
20210903T091819.177599Z | INFO | storage.WalletStorage | saved c:\users\myuser\appdata\roaming\electrum\wallets\wallet_test_multisig
20210903T091819.177599Z | DEBUG | util.profiler | WalletDB._write 0.0097
20210903T091819.690784Z | INFO | daemon.Daemon | on_stop() entered. initiating shutdown
20210903T091819.694777Z | INFO | gui.qt.ElectrumGui | closing GUI
20210903T091819.697766Z | INFO | daemon.Daemon | stopping all wallets
20210903T091819.701760Z | INFO | daemon.Daemon | stopping network and taskgroup
20210903T091819.701760Z | INFO | network | stopping network
20210903T091819.714715Z | INFO | daemon.Daemon | taskgroup stopped.
20210903T091819.741129Z | INFO | interface.[electrum2.taborsky.cz:50002] | disconnecting due to: CancelledError()
20210903T091819.741129Z | INFO | interface.[skbxmit.coinjoined.com:50002] | disconnecting due to: CancelledError()
20210903T091819.741129Z | INFO | interface.[xtrum.com:50002] | disconnecting due to: CancelledError()
20210903T091819.756093Z | INFO | interface.[e.keff.org:50002] | disconnecting due to: CancelledError()
20210903T091819.758086Z | INFO | interface.[b.ooze.cc:50002] | disconnecting due to: CancelledError()
20210903T091819.760077Z | INFO | interface.[bitcoin.lukechilds.co:50002] | disconnecting due to: CancelledError()
20210903T091819.833538Z | INFO | interface.[vmd71287.contaboserver.net:50002] | disconnecting due to: CancelledError()
20210903T091819.899769Z | INFO | interface.[169.0.140.101:50005] | disconnecting due to: CancelledError()
20210903T091819.971348Z | INFO | interface.[bitcoin.aranguren.org:50002] | disconnecting due to: CancelledError()
20210903T091820.047437Z | INFO | interface.[btc.ocf.sh:50002] | disconnecting due to: CancelledError()
20210903T091820.047437Z | INFO | network | taskgroup stopped.
20210903T091820.048407Z | INFO | daemon.Daemon | removing lockfile
20210903T091820.048407Z | INFO | daemon.Daemon | stopped
20210903T091820.099487Z | INFO | plugin.Plugins | stopped

Start with plugins/cosigner_pool/qt.py at send_messages_task line 209 and the logged update-checker certificate failure. Reproduce the cosigner-pool send on Windows 10 with Electrum 4.1.5 and inspect the certificate-verification path. Done means the reported SSLCertVerificationError is explained and the issue has a concrete, reproducible resolution.