_thread Issue with HTTPS

I've been using _thread to run a background task, and at one point the background task posts some data online (so, connects to the wifi, HTTP request and print the result). First time it works well, but whenever I repeat it, I tend to get a number of errors, the main one being
mbedtls_ssl_handshake error: -4290
and
File "urequests.py", line 111, in post File "urequests.py", line 96, in request File "urequests.py", line 60, in request OSError: [Errno 5] EIO
I assume this has something to do with the thread trying to access the wifi twice, as it works the first time, every time, but 2nd time around, no joy.
I have tried wlan.disconnect(), and wlan.active(False) to disable the wifi in between requests, but without much joy.

This is my function:
def postJSON(j, url, retries=0, max_retries=4): data = ujson.dumps(j) if retries < max_retries: # Only retry the connection 3 times, otherwise, give up TODO: Don't give up silently! wlan = network.WLAN(network.STA_IF) if wlan.isconnected(): # Check connection print(data) r = requests.post(url=url, json=j, headers={"Authorization": "Basic " + authkey}) if (r.status_code == 200): # Check if the response OK print("success") wlan.disconnect() return True else: # Otherwise, retry postJSON(j, url, retries+1) else: do_connect() postJSON(j, url, retries+1) else: print("Tried 4 times, and failed. Sorry\r\nGiving Up") return False

Running this on the main thread throws up no such issues.

Start by reproducing the _thread background request using the supplied postJSON function, then read urequests.py around lines 60, 96, and 111 and inspect the network.WLAN and do_connect calls. Compare repeated requests from the main thread and background thread, including the reported mbedtls_ssl_handshake error and OSError. Done means the repeated threaded HTTPS request completes reliably or the failure is documented with a confirmed scope.