I believe the gas tube channel is driven in to the key and pinned. You can kinda see that in the photo. So maybe that part is replaceable? I'll have...
Don't even get me started on how many carriers Ive seen deadlined because someone tried stuffing some Q-tips down the carrier key to try and "clean"...
This is sounding a LOT like a chamber issue. Being essentially a new barrel, I would suggest a good chamber polishing before sending the barrel back...