The client cannot connect to the conference until it reconnects to the server.

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Expected behavior
During group calls, it is expected that all participants can join the conference without issues on the first attempt.

Actual behavior
In reality, some users—possibly different ones each time—may fail to establish a call until they reconnect to the server in the desktop client.

Talk app
Talk app version: 21.1.0

Custom Signaling server configured: yes

Custom TURN server configured: yes

Custom STUN server configured: yes

Server configuration

Operating system: Ubuntu 24.04

Web server: Apache

Database: Maria

PHP version: 8.3

Nextcloud Version: 31.0.2

List of activated apps:

activity: 4.0.0

admin_audit: 1.21.0

app_api: 5.0.2

auto_groups: 1.6.2

bruteforcesettings: 4.0.0

calendar: 5.3.3

calendar_resource_management: 0.9.0

circles: 31.0.0

cloud_federation_api: 1.14.0

comments: 1.21.0

contacts: 7.1.3

contactsinteraction: 1.12.0

dav: 1.33.0

deck: 1.15.1

event_update_notification: 2.6.1

federatedfilesharing: 1.21.0

federation: 1.21.0

files: 2.3.1

files_downloadlimit: 4.0.0

files_fulltextsearch: 31.0.0

files_fulltextsearch_tesseract: 27.0.1

files_pdfviewer: 4.0.0

files_reminders: 1.4.0

files_sharing: 1.23.1

files_trashbin: 1.21.0

files_versions: 1.24.0

firstrunwizard: 4.0.0

forms: 5.1.0

fulltextsearch: 31.0.0

fulltextsearch_elasticsearch: 31.0.0

groupfolders: 19.1.1

ldap_contacts_backend: 1.11.0

logreader: 4.0.0

lookup_server_connector: 1.19.0

nextcloud_announcements: 3.0.0

notes: 4.12.1

notifications: 4.0.0

oauth2: 1.19.1

onlyoffice: 9.9.0

password_policy: 3.0.0

polls: 8.0.4

privacy: 3.0.0

profile: 1.0.0

provisioning_api: 1.21.0

recommendations: 4.0.0

related_resources: 2.0.0

richdocumentscode: 25.4.202

serverinfo: 3.0.0

settings: 1.14.0

sharebymail: 1.21.0

spreed: 21.1.0

support: 3.0.0

survey_client: 3.0.0

systemtags: 1.21.1

talk_matterbridge: 1.31.1026000

text: 5.0.0

theming: 2.6.1

twofactor_backupcodes: 1.20.0

updatenotification: 1.21.0

user_ldap: 1.22.0

user_saml: 6.6.0

user_status: 1.11.0

viewer: 4.0.0

webhook_listeners: 1.2.0

whiteboard: 1.1.2

workflowengine: 2.13.0

Insert your server log here

During the failure, the following output is observed in the coturn server log:
user <>: incoming packet message processed, error 401: Unauthorized

On the signaling server side:
2025-06-24T11:03:13.526543+03:00 bpms-nc-ss01 janus[1049944]: [WARN] [4536513607423791] Failed to add some remote candidates (added 0, expected 1)
2025-06-24T11:03:13.526625+03:00 bpms-nc-ss01 janus[1049944]: [WARN] [2157363314292652] Failed to add some remote candidates (added 0, expected 1)
2025-06-24T11:03:13.548205+03:00 bpms-nc-ss01 janus[1049944]: [janus.plugin.videoroom-0x780888002a00] Data channel available
2025-06-24T11:03:13.650568+03:00 bpms-nc-ss01 janus[1049944]: [4536513607423791] The DTLS handshake has been completed
2025-06-24T11:03:13.650685+03:00 bpms-nc-ss01 janus[1049944]: [janus.plugin.videoroom-0x78088804d850] WebRTC media is now available
2025-06-24T11:03:13.650739+03:00 bpms-nc-ss01 signaling[1050028]: mcu_janus_subscriber.go:78: Subscriber 4536513607423791 received connected
2025-06-24T11:03:13.650782+03:00 bpms-nc-ss01 janus[1049944]: [2157363314292652] The DTLS handshake has been completed
2025-06-24T11:03:13.650807+03:00 bpms-nc-ss01 janus[1049944]: [janus.plugin.videoroom-0x780888007260] WebRTC media is now available
2025-06-24T11:03:13.650967+03:00 bpms-nc-ss01 signaling[1050028]: mcu_janus_subscriber.go:78: Subscriber 2157363314292652 received connected

Start by reproducing the first-attempt conference failure with the configured custom signaling, TURN, and STUN servers. Compare the coturn 401 Unauthorized output with the Janus warnings about remote candidates and inspect the connection sequence. Done means all participants can join the conference without reconnecting the desktop client.