PE 2023 - Playback Window pixelates when video in timeline is altered.

Video playing OK in main window when first put onto timeline. But as soon as effects are added e.g transitions or text, the video is pixelated. Its OK after rendering but I didn't need to do that on previous versions of PE.

I have the latest graphics drivers installed on an i5 Dell PC with 8Gb RAM and 1 SSD drive. 

19th December: This is still a problem.

Am I missing a setting for the project?

Is there a bug in PE 2023 or is it a limitation?