Once I got it off I figured out what happened. The pan is within spec on the sealing face, I did level it slightly, perhaps 5/1000ths or so... at one point. I put a tiny bead of RTV between the pan and gasket just for peace of mine, not enough to leak out and get into anything.

What they did when re-installing things is they mis-aligned the pan and tightened the side in the right rear that was over the sharp edge of the mating surface on the case, this cut the gasket down the centre. The new one looks good, going to put it up on ramps as high as I can get it overnight to make sure.