Hi.
I'm having som wonky behaviour with trimming. In the attached model I have a shelled surface and two trim planes.
But I can't trim the brep. It works sometimes, but mostly the whole brep is just removed. Ie trying to do the same trim several times, yield different behaviour.
Same issue on both desktop and laptop PC and both Moi 3.0 and latest 4.0 beta. Trim works fine in Rhino.

Bests,
Morten