i thought the intended solution was to grab a block from the previous room to finish the staircase.... it makes the cutscene with brooke really confusing....
also on my first time the cutscene triggered when i was standing here, after i killed the slime, and after the cutscene asha was stuck running to the right automatically..... im guessing since she never hit the thing in the block pit that stops her movement
it took me a lot of experimentation to figure out the intended way to trigger the cutscene.... its like you touch the top left edge of the pit and it triggers after a short time? that kinda makes sense but i think its easy to just mess around for a while and never try jumping there.....