One option would be to set "set object physical motion " to false when they release it, that way when they lower one is grabbed the physic engine will not send the one on top flying. This will stop it from falling down if the lower blocked is removed...

I would go to https://www.facebook.com/FacebookHorizon/creations and restore an older version before you duplicated everything in there.

If you ever needed to restore to a previous point, you can go https://www.facebook.com/FacebookHorizon/creations and restore a backup copy.

Not sure what the limits are, but i was having issues editing one of my grouped objects. couldn't ungroup it or pull in another object into the group. So I think there is some bug causing problems.