Why does my Thunderbird 68.7.0 Thunderbird keep closing new emails within seconds of me opening them? I always have to open new emails twice.

I open the minimised Thunderbird ((or newly opened) to check my emails and within 3 seconds of opening a new email, Thunderbird closes it again. I have to open it a second time before I can read it. I have tried several 'fixes' from a reply before and it made no difference. Is there any fix for this? - it's extremely annoying.