Try a very simple project with no 3rd party plugins, codecs, luts, then see if that even imports successfully at all. it could be missing those, so that’s the next variable.
you may also want to try adobe cleaner to do a fresh install with the latest os updates. but technically, I would hold off until you get further variables isolated.
also post as many specs as you can about your OS, adobe versions, effects used, so others can help you. I am walking completely in the dark here.