My setup is:
OSX: Monterey 12.0.1 (21A559),
Processor: 4,2 GHz Quad-Core Intel Core i7
Memory: 64 GB 2400 MHz DDR4
Graphics: Radeon Pro 580 8 GB
I created a new project with Video track: H.264 - 30 fps - 22596 frames - 2048x1152 pixel - MPEG 4
Project plays fine, until Video Player window is opened.
When Player Window is opened, it stays black for seconds and project is hangs for seconds.
The same happens when I reallocate the cursor to different position, and video is not played anymore – I see a frozen video frame, but sound plays.
If I close Video Player, Cubase hangs for minutes trying to close it, or hangs forever, but audio is still playing.
When Video Player Window is closed, then Cubase works as expected.
Other related symptoms:
When resizing Video Track, it takes minutes to recreate (zoom, or redraw?) the thumbnails for the video, but navigation and playback works as expected.
P.S. I suspect that devil hides in video format. If it is true, then Cubase developers should forbit loading it, or optimise/fix this problem.