[exray]

Ugh, I see what you mean. Report back if the dynamite doesn't work

FWIW, I've had my best luck with caps like that using copious amounts of carb cleaner worked in between the shafts. You'll have to remove it from the chassis of course. I''d bet a good ultrasonic cleaner could deal with it if you have that option. The thing looks brand new so I'd guess that dried grease inside is the culprit rather than wear.

I'll be standing by for other ideas...