Hi,
I can easily reproduce this bug. Snaps work on selected objects, even though those objects are occluded. That’s very useful!
Still, if those occluded objects are inside blocks, snapping fails, even though the block is selected.
(By default snapping should work on Selected Objects, in both cases (occluded, not occluded) if objects are selected, but blocks make an exception)
You can see this in the images below:
-
Same block, selected:
Snaps work if not occluded.
-
Same block, selected:
Snaps do not work if occluded.