I have a few RTI and Classic Records pressings that are raising up around 1-1.5 mm on the edges for about a 1/4 of the way into the record. So not quite a massive bowl warp, but still not flat. The cartridge can track them fine and there isn't an audible warp sound like thumps. I'm not sure this is considered enough of a warp that a flattening device would do any good. Unfortunately the few records that exhibit this are long out of print.
However it does change the VTA of the cartridge. I've noticed for some vinyl this changes the sound of them (relative to the non-raised side). Others not as much.
However it does change the VTA of the cartridge. I've noticed for some vinyl this changes the sound of them (relative to the non-raised side). Others not as much.