[Frank Kruse]

Thanks for confirming. I don't see this in connection with video engine issues. In fact I haven't had those in years.
But the pattern is always the same. Auto too dense (which it isn't) followed by the -20021 error and then game over.
Close and re-open session and it's back to normal.
Me and 4-5 other editors on our project get these. Some days with zero issues others with constant errors.