How frustrating! I've been having similar issues since the first of 2020 release. I've had this issues all through High Sierra and Catalina. I'll be curious if someone comes up with a solution for you. Have you tried exporting in Software Only? Supposedly that sometimes works, but that's never helped me on Apple computers. In your example, is it just the text that is messed up?
I ended up figuring out the solution on my own haha. So, the video I was having trouble with was a screen capture. It had a variable frame rate which was causing the issue. I used a converter to convert it to a constant frame rate and once I imported the converted file, my issue was fixed!
Very newbie mistake, but I'm super new to editing so I'm not even a little surprised haha.