Sequence playback is grainy/ gridded - Premier Pro, all video resolutions

Hi everyone! I am at my wits end trying to figure out what is going on with the sequence playback. The problem started after I updated from version 14 to the newest one, and an hour with Adobe chat got me absolutely nowhere. 

Before the update Premire pro played back files without any issues at all, from low res to 4k. Now, ALL file sizes and resolutions have the odd grid pattern seen in the attached image. the grid pattern moves around/ is inconsistent. I tried reverting to the oldest version I could, 15, and it didn't fix it. Sigh. So so frustrated since it was working perfectly before the update. 

I tried messing around in sequence settings and with full res playback, and no combination of settings made it go away. Updated GPU drivers from the nvidia website, and running the creative/ non-gaming driver, too. Changing playback resolution helped a little for some clips (going from full to 1/2), but for most it is no improvement or marginal at best. 

System: Windows PC (windows 10). Nvidia 2070 SUPER graphics. 32 g RAM. 

Thank you for any ideas you have!!!