Black rubber seals - use corn starch - and they are not the seals, but they are the wipers. Their main job is to wipe moisture off when retracting. The seals are actually around the frame of the slide.
It could be that the tracks that the slide move on are dirty and need a good cleaning. Use only Dry Lube on those tracks. Any petroleum based, or wet lube, will attract more dirt and grime.
If by sticking you mean stopping and then starting after a few seconds, well that has been addressed many times and is typically associated with the 50 amp circuit breaker near the motor not being strong enough for the current draw.
Of course, I have to ask, what do you mean by "sticking?"