[dwcsr]

I see on this spindle an spot where it was bashed with something and left an over hanging edge where the bearing may need to seat. That edge is flattened so something tried to press up against it possibly the bearing. If this raised edge were there when you installed the parts this could cock the bearing or make it feel tight until its driven a few miles and it would loosen up. I also see that both those bearings have spun on the journals so you may have what appears to be good bearing with a bad internal bearing surface.

If the spindle was damaged and the bearing was falsely seated and then loosened up by driving it could cock the bearing and if there is internal race damage it make the bearing lock and spin the lock setup. It also looks like the keyed tang isn't long enough to fully engage the keyway.

I'd cut the cage apart and see what the cone race looks like. What do the inner races look like. They would show damage as well but maybe not as much.