Last time I got drums from Rock Auto, the sticker on the side had several manufacturer's names, and their respective part numbers. You hear that they all come from the same Chinese factory, but I've never seen it so blatantly published. Anyways, they warped on the first drive to work. Had the ones that were on the car turned, and been driving with those since.
Sounds like they need to be heat treated to stress relieve them before checking them for roundness and then turning.
Years ago we had our ring and pinions heat treated to stop them from cracking. Was really inexpensive.
