I would think it would easily be possible to have a heat affected zone, or some potential damage to the barrels in that area. I would also suspect that the maker would be well aware of what's happening and might use heat treating options to address it. On appearances, if a ring bulge were to let go, there might be some advantage to directing the majority of force at another part of the gun rather than randomly.

I'd still overall be curious if the lower barrel mishap could cause an upper barrel obstruction. Or, if this is a near simultaneous double obstruction.