Bug: if you have two overlapping objects and click on the overlapping part the topmost object is not picked as expected. I'm using "on object clicked" and a family. If you instead use it specifically on each family member it works fine.
It looks like an old bug since I've found several posts about it in the forum.
It's the same in every broser I've tested: IE, Firefox, Chrome, Opera.
Here's a capx of the problem
Edit: solution/my bad:
I've totally missed this feature, it works adding extra condition "pick top instance".