2020 iMac Screen Glitch on Shutdown

Greetings, just got a new 2020 iMac, 10-core i9, 5700XT 16 GB. It's running BigSur 11.1. I experience a weird screen issue when shutting down. The screen splits in half with the left side having a different hue. Tried it with a solid desktop color (instead of photo) and same issue. When I connected second monitor (TB Display) and shut down, the screen glitch was visible on the iMac only, not TB. Interestingly, when I turn the machine on and shut it down within say 5-10 mins NO split screen/hue glitch. But as soon as the Mac is working over say 15 mins, the glitch is evident on each subsequent shut down. I haven't observed any other issues, but to be honest I haven't ben using it much yet. Of course, I tried PRAM/VRAM, SMC resets, as well as OS reinstall, and no issues. Nothing came up on D scan. Is this a software or hardware issue? I can still return the Mac, but it would be a pain. See photo attached and thanks for any helpful suggestions, best, P.