Black screen on random parts of the video (Nested sequences)

So, I've had this problem for years now, but always found some way to work around it without fixing the problem.

I edit a video and when I'm done and wanting to export soon, I notice problems with nested sequences. I know there have been a lot of similar, solved cases, but none of the explanations helped for me. It's not like Premiere can't find the clips, just random parts of those nested sequences are blank. If I click on the sequences that are making problems, the clips inside look perfectly fine. This has costed me countless hours over the years.

Thanks in advance!