Whatever you do dont take the kybd apart.  The trouble is likely dirty contact wire or the like.  

Did this problem suddenly show up or is it on a new 33 that you are working on?  

I have attached a pic of what I believe is contact wire #4.  It could be the next one to the right.  Both single contact wires.

Zoom in.

Answer the question and we can move on from there.

73,

Wayne

KB1FDW