OK. I first tried turning off PDVD MPEG2 DXVA from the Start menu which didn't make any difference. Then I updated to Cat 9.5, which didn't make any difference either.
I found another bug. It seems that ffdshow is installed with Resize and Aspect enabled and set to "Resize to screen resolution". Unfortunately, it took the resolution from my monitor (Display 2 - Primary, 1280x1024), rather than the display that MP is working on (1280x720), which resulted in the video not filling the screen and caused some head scratching until I worked out what was going on. I've specified the size manually now which is working fine.
I found another bug. It seems that ffdshow is installed with Resize and Aspect enabled and set to "Resize to screen resolution". Unfortunately, it took the resolution from my monitor (Display 2 - Primary, 1280x1024), rather than the display that MP is working on (1280x720), which resulted in the video not filling the screen and caused some head scratching until I worked out what was going on. I've specified the size manually now which is working fine.
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