OK so the error here is:
t=2021-12-08T18:08:21+0100 lvl=dbug msg="Failure for websocket operation: 44ffa23a-3c38-4144-827c-5c2fbb45f4bd: Timed out waiting for connections"
Which was introduced in LXD 4.20
Did you also record the log for the sender/receiver (we’re missing part of it at least).
It may be that error is a side effect of the error you’re seeing about websocket failing to negotiate, as we would then expect the other side to time out when waiting for the connection.