26.3.0 build 61.

What are the complete computer specs, including hard drives (how many, what kind, what is on each, what capacity, and how full)?

Delete the Media Cache and Media Cache files:

https://community.adobe.com/t5/premiere-pro/faq-how-to-clear-your-media-cache-in-30-seconds-in-premiere-pro-2020/m-p/11017257/thread-id/260446?page=1

If that doesn’t work, try updating or rolling back your graphics driver directly from the video card manufacturer’s site. If NVIDIA, do a clean installation of the latest Studio Driver (NOT the Game Driver).

If that doesn't work, try creating a new project and import the old one into it.