If it goes out fine, then most everything is good. But there is a possiblity the controller has a weak relay on it Very basic description way simplified
imagine two SPDT relays with the motor hooked to the moving contact one lead to eah relay
The Normally closed relay contact is ground, so as it sits there both sides of the motor are grounded and there is no operation (Normal)
Push the IN or OUT button and one or the other relay pulls in , the Normall OPEN contact is battery _+ so now the motor moves, which direction depends on which relay. If the "IN" relay has a dirty contact. Well it's going to be slow.
That said NOTE this is way simnplified, not sure they are relays, but I'd think the 10 amps that motor draws running (over 30 starting) would burn out a dirty contact in like nothing flat.
I would lubricate. And see what happens..
Also inspect the slide.. Go out and sit under it, Look toward the OUTSIDE wall (from underneath) You will see a metal L bracket with a line of screws ... Are they all nice and snug? (Guess what my problem was). Look for anything else that does not look right.