Editing a Mac Screen Recording in Premiere Pro causes image fragmentation
I see 2 likely causes:

I think Premiere still supports only frame rates up to 60 and your videos may be recorded with higher fps. Premiere tells you what the fps is, for example in Source Monitor, right click on Properties. Or in the Project Panel, you see the fps (you may have to scroll quite a bit or add the column if it's missing). If your material is beyond 60 fps, try converting it with any other tool, like ffmpeg.

Other users recently asked similar questions (see [1], [2]), so I wonder if there is a bug in Premiere or certain graphics driver versions. If so, you could try to install a slightly older version of your graphics driver. Otherwise maybe contact Adobe support.