In one of the pictures, it looks like the boat is sitting on bare wood bunk boards. if that is true, you need to replace the Carpet. The boat will slide easier.
FYI, the originall plans came from me for the 23.5, designed the mast raise pole system, and was present when the trailer was being designed. l was a dealer who introduced that boat and sold quite a few.
As for the bunk supports, I cannot recall if you had three or four supports on each side for the bunk boards. Can you advise the year of the boat and manufacturer of the trailer. Again, is there any carpet on the bunk boards?
The boat dry wieght is 2000 pounds without motor and gear but displaces 3000 with the water ballast. The bunk boards carry the wieght of the boat on the trailer as it does not have a keel tray for that. you have a centerboard weighing about 100 t0 110 pounds that sits on a tray while on the trailer.
I use to instruct everyone of my customers to store the sails prior to coming to the dock. The centerboard has to be raised all the way and the rudder partially up. Best to open the water ballast and then secure the boat to the ramp. Go get your trailer. Please note that the shallower the ramp is actually makes it more difficult to retrieve the boat as the back of the bunk boards are curved upward. Once on the trailer, you might try motoring to full max to see if you can push it up any and of course winch it to take slake out. Pull up the ramp a little and let the water drain out. It takes about two minutes and then pull up to the parking area making sure there are no overhead obstructions. Then take mast down. i found it was easier to pull forward and then braking. Rick Webb is correct and his idea of something on the back of the trailer to keep the boat from coing down is a good idea.
I also sold MacGRegor, Beneteau, Catalina, Com Pac, Precision and several others.
Be glad to talk with you if want to. Send me a private message with phone number and location. Once a fellow said to call at 8 a.m. which I did. He did and his wife blessed him out. I am on the east coast and he forgot to tell me to call 8 a.m. Honolulu time.