[tunabreath]

More bad news.

Upon disassembly and inspection, it appears the tape on the outer barrel has not stopped the holes on the outer barrel from deforming. I've filed off the ridges forming around the holes, re-taped and reassembled. The inner barrel has also sheared off the lugs in the hop up chamber that are supposed to hold it stationary.
A note for other owners, the immediate symptoms of the outer barrel deforming are that the slide will rub and catch the (now enlarged) hop up unit midway through the slide travel if you rack and release very slowly. It doesn't seem to have any effect operationally (there is only superficial wear on the inside of the slide where it rubs).

As for the blowback chamber, not only were the screws loosening off but the two pins that supplement the screws holding the rails onto the blowback chamber have sheared off as well.

Despite all that, the pistol seems to be performing solidly as ever. I'll keep running it on propane to provide some idea of longevity on it.