Hearing a story like this is a bummer each and every time.
As far as I know, only Sony makes these parts. So you’re stuck dealing with them. Most of their attention seems to now be focused on the newer WH-1000XM2 model, and I’d bet that they want to pretend the first revision never existed. It was a critical winner, but this issue was much more prominent than anyone expected it to be.
I’m sorry I don’t have a better answer for you. I’d either make a warranty claim, or return them if you still can and try the newer model. Thanks for reading.