guess this is just a glitch in rhino 7 which will probably be resolved in one of the next updates, in any case for the record:
I’m experiencing weird issues with the orientation of surfaces on imported solids (from solidworks, both as .stp and .sldprt) in rhino 7.
First noticed this since we use a grasshopper definition to orient the largest surface of a brep on the xy plane and suddenly some objects ended up below zero.
Showing the backface color confirms this:
explode + join fixes this, but is not practical for multiple objects and deconstruct brep + join in grasshoper doesn’t seem to fix it reliably, checking for volume center < 0 and rotating them.