[Mapping] Vaal Foundry - Finished boss but got disconnected

Right after finishing the boss to clear the remaining mobs at the end of the boss area, I got disconnected. I was expecting I would still have an access on the lever to go down, but seemed that I cannot interact on it any longer. I cannot complete the map because of this. During mapping, I did not use any portal back to my hideout so my only way was from the start, to which I traversed (see screenshot below):





Solution for the devs: Need access FROM and TO the platform before the boss fight.