Newbie help part 2, Roland pg800 controller

Hey, a short while ago you guys helped me fix my Boss "hand clapper".
Thanks!

This time I'm trying to repair my pg800 controller. The problem is
that when you shake it (sometimes you barely have to touch it), it
chances some radom parameter.

The first problem is that I can't even take it apart. I've removed
all the slider caps, but I don't know how to remove the rotary
buttons? I've tried pulling real hard but non of the 3 knobs moved
even one tiny bit. I even tried to use pliers.

The knobs look like this:
http://www.bgst.dk/knobs-pg800.jpg

and the backside of the pcb:
http://www.bgst.dk/pcb-pg800.jpg

Is it possible that knobs are glued to the pots so I have to unsolder
the pots? Or what would you guys try to remove the knobs?

I've trie to examine the backside of the pcb without I couldn't find
anything wrong.

Any ideas what to do?

 

Do the orange dotted faces remove to reveal a collett nut ?
If no grub/set screws then presumably splined shaft these days and small
kit.
Looking at a new/unused one determine the direction of the slot relative to
the end positions of the pot.
Turn the knobs to an end position
Surround a knob with a strip of leather and squash the knob slightly ,
initially, across that slot with engineer's cramp/small vice/
mole-grips/lock jaw pliers to squash the slot a bit.