Vaal Foundry Map Boss lava preventing completing the map

If you kill the Vaal Foundry Map Boss before defeating all the rare monsters, lava blocks your path, preventing you from backtracking to clear the remaining mobs and complete the map.

A workaround for this, until they can fix it, is to after killing/looting the boss, just exit to character select, log back in to character, go through your TP, and you'll be back at the start (Or wherever you moved the TP too), as long as you don't put it down in the boss room.

This is an issue with several different bosses, where you can get locked into their arena after killing them, I've made a habit of dropping a TP right outside the boss area, so if I do get blocked in, I can do the above and be right before the boss room, and finish up the map.