Magma Peak Hard

[Skally]

I'm stuck in room 16893. I have saved and explored both left and right on the upper and lower level but the only 2 things that I can think is that I've missed a pink key to go right down on right (but have been back and explored all the level above and I'm sure I haven't and cannot get to the pink key in this room because of a rock fall (or whatever it's meant to be) so all I'm left with is opening the grey door but I cannot find the trigger and I've even been back up and tried to repull every lever.

Could somebody please give me a hint>