thunderbird not displaying select emails

I hope you all are well!

I´ve been having a problem with thunderbird for a while now and today took the time to do the troubleshoot and checked all the account settings. no firewall, no add ons Researching the problem i came across the incompability of different TLS standards. Apparently when thunderbird updated to 78.0 in 2020 a lot of people had the same problem and solved it by downgrading . Since this problem came on suddenly, possibly when thunderbird upgraded automatically, and it only applys to select emails (about half) I guess different TLS standards, some of which are no longer supported by thunderbird, are the reason for this. If i log in to my mailaccount I can see all the emails, same goes for my mobile devices. That´s how i know thunderbird doesn´t display all the messages. My question: Did anyone else encounter this problem? Did I analize this correctly or did I overlook something? I don´t want to change to another provider. I always liked thunderbird for being simple and clean. But downgrading won´t be a sustainable solution either I guess. Thanx for your help. Have a nice day.