Metahuman used with Advanced Locomotion System - Strange cloth movements

Really cannot tell from just the video.

Try removing all the cloth paint.
Then test.

If it works, then the problem is the paint or paint related.

If it doesn’t, then like you say the retargeting is off/bad.

There are way too many bones in metahuman to make heads or tail of it without going hands on, but at least you know that is what you need to fix.

In general, I would never use runtime retargeting unless the coat needs to support vastly different characters (and even then, really, I would rather duplicate the model and weight paint it to the proper extra bones so that the motion is perfect and not some sort of engine driven approximation even if Control Rig can help).

If you set it up right, you simply retarget the skeleton of the coat to the skeleton of the character;
During the process, you set up the bone associations manually / or rather you throughly reviewiew the values the engine chose for you.

If cloth paint is not the issue then the retargeting uses a wrong bone for the upper arms.

Refer to the old stuff for what things should work like

The newer engine is a bit of a dud really…