Okay so anyone suffering from the same problem the solution for the above is this:
editor quality preset.
-It forces low LODs to improve performance,
-metahumans cut the number of bones on lower LoDs,
-mesh with fixed LoD tries to look for the bones to copy the pose or set their own transform,
-can’t find them in between the ends so for a shirt the wrist and neck area look perfect, anything in between gets distorted or does not animate at all
-increasing LoD increases number of bones in metahuman model, with ‘high’ editor quality preset reaching the proper number.
Fix is easy, custom LoDs for every armor (obviously, would have done it anyway) and/or weight paint the bones that are permanent on every LoD and kinda skip the ones that get removed on lower quality levels.
Interesting find, #FeelsGoodMan.
Edit: one more thing, its view distance.