New messages in the currently watched channel or private message do not appear unless a) manual refresh b) channel switch c) wait for some minutes.
Other topics with similar issues did not provide a solution to this issue.
Steps to reproduce
Watch a channel. Let someone post a message into that channel. You can also try it with private messages, the issue is the same.
The new message appears without delay.
The new message does appear only after a manual refresh, after waiting a real long time (several minutes) or typing a message yourself (I guess this triggers a refresh). Logs (put on debug level) do not show anything related or otherwise noteworthy. Browser network console shows a successful websocket GET request with 101 return code and no errors. Push notifications work as desired.
Tested on current Firefox, Desktop App and iOS mobile app, all showing the same behaviour. The issue first appeared after upgrading to 5.0 and persisted through all updates until 5.6 which we are using now.