One thing that I don't think I saw was a bent housing. Tapered bearings can run loose enough to not be affected by a mildly bent housing. But ball-bearings have no such forgiveness. If they are forced out of alignment, they will squeeze the grease out, and run steel on steel, making plenty of heat. But if your housing is bent enough to cause that, then your installer would surely have noticed it, as he was "hammering" the axles into the tubes.