For me it appears that anything I just "drop" into place from my inventory will stay in place as long as I don't touch it. If I pick it up and manipulate it (especially using the workshop interface) it will drop through any table/floor etc...
A real shame, since using the workshop interface is MUCH easier than trying to pick it up manually.
Beth has been having issues with item placement/decoration in every game of theirs I've played.
I just don't understand why it is so hard to fix, or why they can't at least give items a semi-realistic weight/rotation when you "pick them up" manually. Why do nuka-colas always have to drift upside down or sideways when I pick them up? They clearly have a light end and a heavy end, just make them "droop" heavy end down....PLEASE!!!!
That said, anyone been able to place nuka colas in a nuka cola machine standing up correctly? It is impossible using the "pick up" mechanic, and even using the workshop interface they are not allowed to be put in there due to clipping or something!! smh...SMH!
And yes, I do know about OCDecorator mod, I will use it, I just usually wait to install mods until Beth patches a few times and the GECK is out, so it doesn't mess up any of my games.