One arms moves with body, other doesn't

Next time you can reduce the size by only uploading the ".puppet" file - it has the complete puppet in it (you zipped up the whole project - which is fine, just bigger than needed).

A few suggestions / comments.

• I imported Niel.puppet into a new project. I turned on webcam and moved my head. Both arms moved fine - so I am not sure what the problem you are seeing. If you import the .puppet file does it work better? Maybe CH corrupted something internally?
• Oh, do you mean you are trying to use physics to make the hands dangle down, so when you move the body, the arms point down? One arm is doing that more than the other. Hmmm. It looks like the shoulder is moving more on one side than the other, and that shoulder movement is what is causing the arms to move.
• If you want to use the "Arm IK" behavior to stop arm stretching, you need to put the "Left Shoulder" handle on the torso artwork, not the arm. You put it where it attaches.
• The arm joint is a pain in CH It *tends* to work better if you draw the arms in an "A" or "T" shape (basically arms out sideways, not straight down).

A suggestion that might help with a few problems, but it requires some minor artwork changes.

• Change the "Attach Type" for the arms from "Weld" to "Hinge".
• For the end of the arm at the shoulder, draw a semicircle on the end. Otherwise you get a gap when the arm moves. Basically add a bit more artwork to fill in the gap that becomes visible when you move the arms.
• To make it look good, you could take a copy of the brown straps (?) near the shoulders and put that copy above the arms. The purpose of this is to hide the end of the arm artwork a bit behind.

Filling in the arm...

Shoulder strap...

Layers

It *might* help.... and depending on how you want to move the arms, it might not!!!  You need to think about where the arms are going to move (in front of or behind the body, and frankly it is finky. 

All I can suggest is a few options and hopefully you find something you like... E.g. maybe just using hinge is good enough (the shoulder straps above might be more of a problem than it solves frankly).

I also tried putting a stick across the shoulders (from the top of one shoulder strap to the other). Both arms are then more consistent. (Maybe not "good", but "consistent"). I think the issue is one shoulder is wider than the other. Maybe a stick on one side only, or down the middle of the chest, might trigger the behavior you want.