Sometimes the less experienced participants are left to the parking & retrieval process, not really knowing or scared, causing a problem. Patience grasshopper.
A coworker once went fishing with me, and responded he could park the trailer when asked. He didn't volunteer that in spite of his affirmative answer, he had never moved a vehicle 20 feet with a trailer attached. At the end of the day, he informed me that a fender on the trailer was crinkled, having contacted a heavy bumper on a truck in the parking lot that he claimed was not damaged by the event. The other truck was gone, and I surely hope it wasn't damaged by the idiot who trashed my trailer fender.