HP, Canon, Brother, Dell, and many others... they all have a problem with sticking solenoids. When they put the machines together, they put little pads on the solenoids to keep them quiet. Those pads disintegrates over time, and then instead of a pad, it becomes a sticker--and it makes the plates on the solenoid stick, instead acting as a cushion.
Technicians have different ways of dealing with this. Some of them just replace the solenoids. The problem with that is there are so many different kinds, and you'd have to keep a wide variety of them for a lot of different machines... or leave the customer down while you order one.