Streaming video on Safari goes black while audio continues

I have had a persistent problem with streaming video from by our cable provider, Amazon Prime Video, and Netflix since the original installation of macOS Big Sur.

Essentially the screen goes black appx 30 seconds into play, although the audio continues as normal and if subtitles were in use they continue. This occurs every time like clockwork, can only return to video for appx 30 seconds if you click out and then back in, but the same problem persists. I have frequently scrubbed through Apple Communities discussions and other internet sources since it began but have found nothing that discusses the same problem.

I am operating an iMac 3.2 GHz 6-Core Intel Core i7, running the current versions of macOS Big Sur, Radeon Pro Vega 20 4 GB graphics, and 21.5-inch (4096 × 2304) Retina display. This problem has persisted since the original Big Sur OS was installed, currently running 11.2.3. The problem does not exist on our MacBook Air running the same macOS Big Sur update, nor on this iMac prior to the Big Sur installation, nor on my previous 2013 version iMac. It also does not exist when running Google Chrome and Firefox on my iMac (at least I have that workaround).

I would be eager to learn if others have experienced it and possible remedies.