Two joint at the same place / Can't retarget animations

Hi, I’m a student currently learning UE4.

I’m actually facing a problem with my character.
First, my character is composed of a main suit mesh (which is like a human body) and different armor plates meshes.

I rigged and skinned it in Maya, using abAutoRig and then this tuto - YouTube .

Another important thing is in my joint hierachy, I have my left clavicule > left upper arm > left forearm > etc… and, in a different “node” I have others joints like left upper arm weight > left forearm weight > etc…
Then, I tried to retarget my character with the ThirdPerson Animations from UE4.
The thing is that I have to select for example the “left upper arm weight joint” to match with the “left upper arm joint” from the UE4 skeleton.
The problem is the “non-weight” joint are still there and don’t move at all, so it makes a weird deformation. For example, in the shoulder, there are 2 joints at the same location where one is correctly moving (the “weight” one) and one is not moving (the “non-weight” one).

I tried to get rid of the “non-wieght” joint in Maya but it mess up everthing…

Plus, the joint in the chest make the armor plate skinned to this joint moving correctly but the suit part under this armor plate doesn’t move so it get through the armor at that location.

Well, I’m lost. I think the problem comes with these “weight” joints but not sure.

Does this already happend to someone ?

If you think I have to rig and skin once again my character, can you please link me a tutorial which will work with retargeting animations ?