Treasure cages

I played Brogue a lot in the past. Beat the game on few different builds.

I picked up the iOS version for a long plane flight.

I have a found couple of caged treasure rooms. I can’t seem to get the cages to stay removed. When I step on the trigger all the cages lift of course, but then they all drop again when I go to get any item in the room. I have tried throwing things, dropping things onto the release mechanism, etc., but cannot get it to stay triggered. Either it’s different or I have forgotten how to do it. Advice?