Problematic things

They are basically what we know from other programs as groups. It's convenient concept which allows us to abstract several objects in a one entity and operate on all of them as on the whole one. The problem that it made VectorMotion crash a lot. So in their current implementation state I don't recommend using groups at all.

But here's more... You can even animate different scenes and combine (if VectorMotion doesn't crash). And it can ideally allow you to make camera movement effect easily: one scene contains your whole animation, the other one displays and slides over it making the whole animation more interesting. (Alight motion has camera movement animations.)

Yes, sure. Sometimes VectorMotion "forgets" about the stroke applied to the object and makes it transparent. Honestly, I don't know exactly why it happens, but I confirm that such problem exists and appears when you reopen your project.

Glassy effect (Background blur as VectorMotion names it) doesn't work perfect: you can't warp the shape (through Bezie deform filter) and expect this effect to work on the resulting shape. It will ignore this warp transformation completely. Which means that you can't bend the object and expect that it will show though blurred background correctly. As a workaround you must avoid using such effects for that: its recommended manually moving your object points (which can be quite tedious) to keep Background blur work fine.