First thing to do is update your Gpu (videocard) drivers. You have an AMD card right? The issue looks exactly like an issue happening with previous drivers for AMD cards.
Let us know if you need additional help, the people on this forum is very hrlpful and will try to guide anyone through their issues with Rhino.
Rhino support pointed me to “Properties…” / “View” / “OpenGL”, where I disabled “Use accelerated hardware modes” - and the problem is gone! But I fear when working on bigger models I get some performance loss when keeping this setting - so it’s only plan B.
Here is a screenshot of my Video Hardware / Driver Information: