Vaal Foundry Boss Room Stuck

In the map Vaal Foundry if the boss is present, it is possible to teleport into the arena using lightning warp but by doing this the arena has no exit to finish the map.

Is it possible to add a switch to the inside of the arena that lowers the lift if you accidentally teleport into the arena?

+1
Vaal Foundry could be bricked if you do the boss before killing ALL the rare mobs. No way to escape the arena after the fight to complete the map. Even with checkpoints, it's outside and can't be clicked from within the arena.

I just experienced this without warping down. I accessed the boss the normal way, but there is a rare left in the map and no way to return up above the boss pit.

First map of the day and this happened to me. Boss was closer than the last rares so I did it first. Now I have to leave it unfinished.