Big thanks to Harry @hk47 for helping me initially disassemble/diagnose my problem.
Fixed it with a $1.75 Shaft and $4.44 Holder Joint (x2 because I did both sides at once, and one side Holder Joint was damaged) from the Audio Technica parts department. I emailed them and they got back to me within a few days. Shaft was on backorder, but over-all experience was wonderful. Also upgraded my earpads while I was at it to make the $10 shipping cost more worthwhile... Feeling like brand new!
[image|3672941]
If your brass rod doesn't want to come out due to burring like this, you can try cutting it with a jeweler's saw, rubbing it with sandpaper, or as a nifty trick, carefully rubbing it on concrete sidewalk/curb to deburr it and let it slide out naturally. You can see in the photo below where I accidentally rubbed the plastic bit for a second or two... Be very careful! Concrete is very abrasive, it doesn't require much! Just try to rub the burrs themselves, not the top or plastic. I used the curb on the side of the road to make it easier.
[image|3672943]
When assembling, if you're having trouble getting clearance inserting the metal clip into the brass shaft, use something in between the shaft and the frame to temporarily push it up. I used a few pieces of sticky note paper that I cut up, about 3-5 layers deep. It made inserting the pin MUCH easier, as the hole as fully out of the plastic holder joint, and was easy to take out after.
[image|3672940]
Here's what it looks like assembled, in my case there is no longer ANY play with the headphones besides the swivel, as intended.
[image|3672945]
You can reference these numbers when ordering from the parts department. They should help you out parts@atus.com. I worked with Kim Netzband according to the signature, and they were absolutely wonderful!