Copper Citadel: Unable to backtrack

After defeating Jamanra in the Copper Citadel, you are unable to return to other sections of the map to do any kind of bonus content you may have passed on in order to reduce your chances of dying prior to fighting the boss.

ref: 3,172,434,559

The other section of the map is destroyed after jamanra cut it off, the arena itself is made of what remains of it. Though i never tried to exit to main menu, spawn in HO and enter map again, did you try this?