Loose knobs on RS-2 Ventura

[psemme]

Hello!
I just acquired a beautiful RS-2 Ventura that sounds amazing.  The only issue is the volume and tone knobs are all wiggly. I opened up the back and the pots themselves are secure.  They all work fine but I'd like to find a way to tighten them.  I applied a bit of upward pressure on one knob to see if it would come off, but it didn't budge, so I backed off that approach.  Any advice would be most welcome!  Thank you.