Squeaky TLR Lens

I have an old Richoflex TLR that I use occasionally and it works great except that when I adjust the focus the lenses squeak and it is sometimes difficult to turn the lens/focus. Is there a lubricant that is safe to use around the lens barrel and on the coupling gears, or should I just live with squeak?

If focus alignment is OK, I wouldn´t do anything.
I wouldn´t try to do anything regarding the camera´s mechanics on my own, unless you are already experienced with such things.
Greetz, Benjamin