Problem with splitting and modifying polysurfaces in Rhino8 Mac

All of a sudden Rhino8 on my Mac is unable to work properly with polysurfaces. I thought it was an issue with the complicated geometries I was working with, but now it is the same with even simple boxes.

Problems include:
– Unable to split a polysurface with another surface
– Unable to Cmd+click and drag individual points and/or surfaces to modify the polysurfaces

Splitting polylines works just fine, and polysurfaces can still be scaled with scale1D, scale2D and so on…

This was working just fine yesterday, and has been since i updated to v8 months ago. Thoughts?