I had the same problem with my Ribcraft - on mine the chines were taller/deeper than the depth of the roller, so unless the boat came up exactly square and on centreline, the chine would push against the inside edge of the rear rollers - where there is a steel flange on the roller axle. It did exactly the same sort of 'chip' damage, in exactly the same place.
(Photos are on here somewhere - not clever enough to find them)
After a lot of messing about - the best solution is to get bigger rollers for the trailer so it simply can't happen. With the current rollers, if it can happen now, it doesn't matter how much you adjust it, it can happen again. Adjusting roller setup/position can reduce it, but you won't stop it.
My rollers are asymmetric, so I just turned the outer rollers round so the chine can't hit the flange. I also adjusted the roller positions to improve the situation a bit.
On the bright side, I'm now quite good at gel coat repairs!!