Recently had the trailer serviced for a stuck caliper and all seems fine now. Prior to this work we could not back up at all without putting the trailer brake key in. We went out to the lake this weekend and it backed into the water fine, thus we chalked the problem up to the seized caliper. However, when we got home and went to put it in the driveway, we had to put the key in to back up. The boat was on a slight incline forward the way the road is if that makes a difference. The vehicle is a 2004 Jeep with the trailer install done right from the factory, thus I am sure it is wired correctly to allow it to back up this type of trailer. Any other thoughts on where to look?

Thanks,