While installing the replacement tank today I looked down inside it. There is a substantial weld/solder on the inside where the outlet flange is attached. The defective tank has no visible evidence of a weld on the inside of the tank at the flange.
I couldn't light the inside well enough to take a decent picture.
I don't know if this means they found the problem and fixed it, or whether this is the normal method of construction and the defective tanks just missed a step in the fabrication process.
We'll see what happens, I guess.
