Can't establish connection to the server at wss://

I am new to Jitsi. I have Jitsi hosted on a privat network. Conferencing works also from outside including audio and video.
In the firefox developer-console i currently see errors:

2021-01-28T15:01:45.609Z [modules/RTC/BridgeChannel.js] <_handleChannel/e.onclose>: Channel closed: 1006
2021-01-28T15:01:51.894Z [modules/RTC/BridgeChannel.js] <_send>: Bridge Channel send: no opened channel.

Logger.js:154:22
o Logger.js:154
_send BridgeChannel.js:383
sendMessage BridgeChannel.js:190
sendChannelMessage RTC.js:936
sendEndpointMessage JitsiConference.js:2519
sendMessage JitsiConference.js:2563
e2eping JitsiConference.js:349
sendRequest e2eping.js:93

Since everything works fine, i am wondering what causes this error message.

I checked all relevant posts on this forum but everything seems to be fine and correct.

Is this on self-hosted deployment? Is this the latest version? Which web-server do you use?

Yes, it’s self hosted.
I used Debian 10 (buster) installation directly from repository.
The webserver is apache2.

You need to convert this rule to apache syntax and add it in your apache config and if it works a PR is most welcome jitsi-meet/jitsi-meet.example at 3f93726c418b262da682280e5fdae0aa6dd4d58f · jitsi/jitsi-meet · GitHub