I duplicated a finished interview project in order to cut a teaser from it. With this project, it first didn't load the videos, then I got about 100 error messages with "Error retrieving frame XY at minute:second". Now one of the two main videos stopped working. It is no longer displayed, the timeline always stops before the "broken" video when playing and only shows black. Sometimes the timeline and the sound keeps running but shows no picture and I can't stop it with the space bar.
What is also worth mentioning is that the error display appeared only once, but no longer when I opened it again. But it still doesn't work now. With other old projects, the situation is quite similar. Normal work is no longer possible.
What is the cause of the error and how can I fix it?
I have already deleted all media caches, reset Premiere to factory settings, restarted the PC, etc. I have already done all of this by Adobe Support, but these measures could not solve my problem and therefore referred me to this forum.
The videofiles are .mp4, filmed with a Sony camera. iMac 2019
MacOS Big Sur 11.2.1
Processor: 3 GHz 6-Core Intel Core i5
Graphics card: Radeon Pro 579X 4 GB Premiere Pro: 14.9.0