Altar of Set 3rd Tier Bug

I think you are mixing two things up here. Since I am PC-player and don´t know about the actual falling through world bug, i can only give you this link:

Concerning the altar-upgrade-problem: To my knowledge, if you build the altar on plain foundations, there shouldn´t be a problem. To me it only occurs if the temple has been built directly on the ground, but that´s on PC.