Problem with Retargeting in Auto Rig Pro

I can’t seem to get retargeting (“Remap” in ARP) to work with my imported Mixamo FBX. I’ve followed the developer’s documentation and video plus Youtube videos by Darren Lile and CGDive. Right now I’m getting weird stretchiness in the left arm (see attached image). I’ve spent hours trying to get this right and it’s still not working. If I was an expert maybe I could fix things quickly but I’m still a relative newbie. I’m starting to think I’d be better off just creating animations from scratch rather than continuing to import Mixamo and running into numerous unpredictable problems. This wouldn’t be so bad if I planned to become a full-time animator, but I’m trying to prototype a product and animation is just one part of it.

Any tips/suggestions are appreciated!

are all rigs and objects correct scale with scale applied? scale can be an issue with auto-rig. other than that I don’t have any guesses currently. Make sure they’re human sized with scale applied.

One tutorial I followed said to click “Auto Scale” at a certain point, so I did. But I’ve run into the same problems without clicking “Auto Scale.”

[Blender] Retargeting/Ramap using Auto-Rig Pro (COMPLETE guide)