I promised not to post except in Scotts Forum but I cant let you hang since I know the issues first hand.
The snap ring is fine, it needs to be seated properly thought, if not done right it can be damaged. If you can bring it to the shop tomorrow I will fix it for no charge. Dont try to remove it anymore though.
You CANT replace the ring, ring tension spring, or snap ring on that setup without destryong the YHM AK Mount. Its pinned to a short barrel, the barrel has to be removed then the mount cut off, then replace the YHM mount, repin, then reinstall the barrel. Its not a cheap job.
When you remove the Supressor, always try to remove it when its HOT, it comes off easier most of the time this way. Use the Bowers Suppressor Cover when its hot or cold, you wont get burned if you only touch the cover. Split it length wise so you can encompass the suppressor, but remove it when being fired. Only use the cover for letting a HOT can rest on an object, removing and installing. It adds alot of grippiness as well.
Use Mechanix Gloves on your Hands when using the Bowers Cover.
Always use antisieze on the ACME Threads and if the can locks up spray WD40 into the gap between the lock ring and the suppressor to leech. A rubber mallet whack a couple times near the mount will break loose the carbon often too. Do it when its COLD because the can will melt the mallet.
You can minimize carbon buildup in the blast chamber by slightly un-ratecheting the can after every 100 rounds and screwing it back on. It cuts out the carbon, its what those aggressive cuts on the flash hiders do, they ream out carbon and minimize contact to prevent carbon bonding.
The issue you are having is common when shooting on a 5.56 mount and swtching to a 7.62 mount. The 5.56 mount is SHORTER and allows carbon to build up in FRONT of the mount. When you try to screw on the LONGER 7.62 mount the carbon is impeding installation. A harsh wire brushing in the blast chamber will break off the carbon.
I can do a video if you need and cant make it to the shop.
If you need more please PM me, I would prefer not to post outside the Scotts Section.