Hello,
I want to retarget animation (from UE4 mannequin) to another main custom skeleton and be able to import other meshes and assign their skeleton to the main custom one.
Our skeletons have the same hierarchy but different proportions
So, I followed these tutorials:
This one to retarget animation from UE4 mannequin to my custom skeleton (it work!)
https://docs.unrealengine.com/en-us/Engine/Animation/RetargetingDifferentSkeletons (different skeleton)
And this one to import another meshes and assign his skeleton to my custom one
Animation Retargeting | Unreal Engine Documentation (same skeleton)
But the problem is that I got an animation that slips… On the first retarget, It’s a little slippery but for the second one, it’s just terrible…
If someone have an idea on how to solve this? 
~Nyudeb