No available transport channel, can't send a message

After I updated jitsi a conference is not working anymore.
I get the message, that somethin went wrong and I can find the following message in the logs:

JVB 2019-09-06 13:36:28.452 WARNUNG: [13] org.jitsi.videobridge.EndpointMessageTransport.log() SCTP connection with 26e23beb03dac87a not ready yet.
JVB 2019-09-06 13:36:28.453 WARNUNG: [13] org.jitsi.videobridge.EndpointMessageTransport.log() No available transport channel, can’t send a message

What happened?
Disclaimer:
This machine has not NAT.