Using Thunderbird Linux for years on my laptop, it sometimes happens that an error message from Thunderbird pops up (mostly because connection problem when I'm in a train or outside, maybe draft can not be saved or whatever). I just so happens, that when I'm writing an email exactly at this moment and press space, the error message is gone before I had a chance to read it. I could even accidentally answer (y)es or (n)o to a specific question if I happen to press y or n at that moment when the message pops up. So, not an everyday problem. For me it's happening like a 2 or 3 times during one year. Not quite sure how it could be solved.