Dear Maintainer,

sometimes messages didn't appear in a groupchat window. Also
"close" window and reopen the chat window did not solve the
issue.

I guess this situation take place, if you have two accounts
joined the same MUC. I used an account for my normal user and a
supervisor (admin) account in gajim. Normally, I'm not connected
with the admin-account. In this situation the admin-account and
normal-account has been switched on. I was not able to see two
messages which has been sent to the MUC, but it appears in the
history-dialog.

Note: The bug report has been sent from another machine, but I
keep system information, because they have more or less the same
setup.