My solution to spinning ball.
First I began emptying the media cache and media cache files folders. These folders are located within the folders you are saving your project files. I moved mine for easier access.
This helped until one day they didn’t. I had been emptying and it usually worked. Suddenly this action was not yielding the results anymore.
I then emptied the .PRV file folder. You can empty these files via the Pr Pro interface (preferences) AND physically place the files in the trash. I did both.
My problems were solved and I have since submitted my video project to client.
Hoping this helps.
Still plugging.