I ended up doing the same thing that you are doing until the end of my project. That particular project was “ABCinema”, so yeah – it was definitely a nightmare. Regardless, ever since, I haven’t encountered the problem again. One thing that I tried in brand new projects going forward that may have helped was that whenever I did import a filmed effect – I immediately right clicked it in the viewport and made it my composition’s frame rate… but in the end, I really think it was just a glitch in the project I was working in on Adobe’s side – not user error.
If it’s happening in other projects that you start from scratch, you may want to try reinstalling the program or contacting Adobe for specialized help.
Hope this helps,
Evan