When you switch to vanilla FP arms while Paper Doll is displayed on the interface, try walking and swinging your hand around and you'll see how your doll is acting a little bit... weird. Specifically, doll holds their arms straight down whatever you do. I guess that happens because hands are fixed for FP perspective right in front of the camera, so they have to be fixed on playermodel itself.

Ok got reported some ways to reproduce this, it seems to be a combination of Firstperson mod + not enough animations + having vanilla first-person active and potentially something in your offhand. I'll look into it.

Hm I've never seen/heard about that, so it could also be linked to a mod conflict? I'll take a look on rather I can reproduce it.

Hm I can not reproduce it, so I guess some other mod is doing something odd with the player model while in first person?

I tried without any other mods, and that still happens. I'm guessing that might be... because of Double hands, perhaps? I didn't try that without Double hands yet