Lots of very strange behavior here in this lava drained room, my miners won't mine any of that normal, unwarm rock designated, and there's carts with lava (invisible ofc, by the lock symbol) that they won't haul either. They have a path there and I've even lead miners down there as a squad before before and they don't do anything, they just stare at the rock if you disband the squad. Interestingly, I couldn't station them in the room directly, they claimed "no access" until I lead them to the first staircase above it that it would let me, then I could station them in the room.

On other saves, I've managed to dig a staircase down as alternative access to the minecarts, but the hauling designation symbol will just flicker on them and immediately go away. You can forbid and unforbid the carts to get it to happen as much as you want. It's like everything around that rooms works fine and you can add as many new valid paths to it as you want but everything in it is just totally broken. World was started on the first release.

Will note: uploaded save is zoomed in on relevant area, and has a remnant of borrow used in an attempt to fix the issue (which are know to cause issues akin to this); I have already tested that it is not the cause of the issue. Removing it or any borrows make no difference to the problems I've described.

Edit: I figure my case must be temperature related, I turned temperature back on (save was saved with it off) and they can haul the (now obsidian filled) minecarts and have access to the room again.