D850 "quad buttons" not working

I'm looking at buying a second hand, dropped D850 with the quad buttons on the left side, on top of the shutter mode knob not working ( mode, metering, white balance, quality ).

I suspect they might be fixable (loose) but if they are not, can these be purchased as a spare part or is the whole upper assembly all in one part (weather sealing).

I can't seem to find a proper tear down that would answer this question.