Notes won't change tempo

I work on a Windows 10, older PC, but this is so basic, it should not matter which PC i'm working on.
If i want to ad a note i cannot change it, it keeps going back to 4 count notes. If i accidentally have a note in my score selected, it will change that note to four counts and it proofs very hard to ctrl+Z it back. I am sorry to say that Musescore 4 is riddles with bugs for me. I never had this experience with Musescore before. Absolutely nothing works properly or smoothly, while my computer still (just) meets the specs.
I tried going back to an older version, only to find that my scores had been altered when downloading 4.0 and won't play anymore in 3. It's not stable and even basic functions like adding notes do not work properly. Been using it with great pleasure for years, so i'm surprised about this update being so buggy.