The elevators aren't prop_physics, only the attached parts, and so I think Adv Dupe is chucking a wobbly at them.
I'm willing to bet you are pasting your dupe frozen and without constraints. Try pasting an elevator with constraints to test. Do not forget to unfreeze and unweld said elevator, else it won't work.
Just working on the logic of, weld = constraint, without constraint = no weld, returning value prop. Therefore, elevator might = constraint, ect ect.
Ive noticed that aswell but its an issue with the tool not LL