I am having the same problem.
I am editing four projects right now.
I finished the first project without any problems.
When I started with the 2nd project, the problem appeared. the video goes offline and it returned to becoming unrendered.
I opened the project that i’ve finished. It turned out to be exactly the same as i left it.
if the problem is with the media cache of my disk, shouldn’t the problem also occur for the first project?