"Intersect" comand freezes Rhino and needs a force quit

I freezes most of the times, unless it;s a simple intersect like surface with a line that will give a point.

I confirm this problem on 5.1 and I stress that this problem also exists in earlier versions of Rhino for Mac, which only occurs intermittently without giving me the opportunity to fully understand the problem and provide the right information. Being a command that I use often, I looked for a solution to mitigate it. 1) avoid creating intersections where there are objects in groups. 2) hide or disable the levels of all the items not used for the intersection. 3) Sometimes, a simple restart of the Mac lets you run intersections that previously led to the blocking of Rhino. iMac with OS X 10.9.5

I’m also having random intersection problems…