I can also confirm that this issue only happens when I have Thunderbird open. On my system, Thunderbird opens messages in a new message window and this is when the problem seems to occur, although it doesn't happen every time.
I can also confirm that this issue only happens when I have Thunderbird open. On my system, Thunderbird opens messages in a new message window and this is when the problem seems to occur, although it doesn't happen every time.