I haven’t read much about the dimensions of the boxes vs. the dimensions of the hallway. I know there is one in the middle of one hall, left there without finishing up in a niche for some reason. Perhaps they made it too big—or just got tired of hammering, eh?
Abandonment probably occurred due to a military or other national crisis. Contrary to the modern agitprop, ancient Egypt was not politically stable for thousands of years. Still isn't.