Thanks Grim, so yeah still unable to get this problem fully sorted, however your final note (disable collision, set platform mobility to static after possess, stop elevator) does work. Which is progress! Earlier when I tried stopping the platform the turret would still jump the first time I possessed it, but not again after. Not sure what to make of this, but its movement in the right direction maybe, haha.
I’m completely out of ideas at this point that don’t involve rethinking the level design and story… Kicking myself for not testing this much earlier in the design but I just didn’t foresee this, of all things, being the preventative issue. Thanks for lending your brain on this, I’ll report back if I find a solve that works for my situation.