Focuser getting stuck

[Granada]

My 2", dual speed Crayford focuser is not rotating freely all the way, and gets 'stuck' (i.e. slightly harder to turn) at the same point during each turn - I have to provide additional force to turn it. Doesn't mater which speed I'm using. What could be causing this and how to fix it?

[Rerouter]

Seems like a good servicing guide can be found here,
http://polluxchung.com/gso_crayford_fix/

My best guess is some damage or mark on the focus tube if its only in 1 location, if its spaced about every 1.5cm then it would be on the roller,

I would say tear it down, inspect for damage, and try and polish or file out any high spots it might be getting stuck on.

[Granada]

Thanks, yes I should have specified better - it's the roller because it's in the same spot every turn (i.e. equally spaced on the tube).