What's causing my armature's simulated bodies to become unaligned with their simulated mass?

I’m trying to make a character with two tentacles on his head like a twilek from star wars but when I have more than one chain of bones set to simulated, all but one offsets from the simulation like this: (Simulated the leg here for testing purposes.)

Notice how the one tentacle and leg are still being simulated in the right place, but shown in the wrong place.

I think this might be a problem with importing from Blender 2.8. But the one person that answered my post on reddit about it is using Blender 2.8 and UE 4.22 and has no issues.

I’ve spent a awhile making sure the fbx I export from blender works. So all scale is applied and matching UE4, armature isn’t called armature, animation isn’t tiny when imported into UE4, etc.

I get the physics asset set up with bodies on all the bones I want, set them all to kinematic with collision and turn off collision between bodies that share constraints. Now if I set one chain of bones to simulated it works fine. I can get one tentacle or limb to simulate. But as soon as I add a second or third chain, the bones offset from the simulation.
Also there seems to be some kind of bias, as it doesn’t matter what order I make them simulated, it will always be the one tentacle that works. If I set that one to kinematic, then it’s the other tentacle that works, like this:

If I set only the legs to simulated then one will work and the other won’t. Any idea what might be causing this?

Here’s some images of the skeleton structure and constraints in case it helps: [Armature][3] and [Constraints][4]

I’ve also tried making a 3rd person project and adding simulation to the player character’s limbs in that. It worked as expected. But when I exported that character, opened in blender, exported a new fbx, and reimported into UE4, the same offset issue happened. I’m not sure what else to try. Any suggestions?