Final Cut Pro

I don't know how to explain this properly but here it goes, I have certain clips that are not fully rendering even when I click "render all." so if I hit play to watch what I have on my time line those clips play glitchy, only way for it to be fixed is to re-ad the original file and delete the old and re-edit the new one. The problem is other files start to do this the next day when I open up the project. If you look at my image uploaded you can see the rendered dots, that's where it plays glitchy. How do I fix this? project is 4k 30fps, files uploadedare 4k 60fps.