8-3/4 Auburn sure grip axle issue

I had to do some brake work, and found a bad wheel bearing, I decided to swap over to the later version green bearings while I was in there.

Car is back on the ground, but has trouble moving, up on stands it works fine, but nothing on the ground. Driveshaft out and it seems fine, dig a little more and find the if I have someone hold the brakes, I can turn the pinion while the wheels stay stationary.

Pull the axles and diff out, take some measurements and it looks like the axles engage the cone and the spider on one side, but not the other.

Axles are, to the best of my knowledge, shortened C body (BBP conversion) and they're standard 27-11/16 a body length.

I can't find any info about an incompatibility with the Auburn factory diff and that axle length, except Mancini. They sell 28" yukons and explicitly say they do not work with the diff in question.

Can anyone shine any light on this?