Here's my secret for working with a repair shop. Doesn't seem to matter if it's a 40-million dollar Gulfstream, a 40-thousand dollar Suburban or a 4-thousand dollar pop-up camper, it's the same drill. Please don't give this secret to any repair facility, because they will immediately develop a strategy to counter-act it.
First, prepare a detailed list of each problem you face. See if you can cause the problem to repeat so you know when it is likely to happen. Do as much testing and observation as you can under varying conditions and situations to identify and isolate the problems. Try to imagine that you are a technician working on the problem, and the trailer is sitting in your shop. Provide all the information you can to speed up trouble-shooting and diagnosis. Even if they don't get it fixed the first time (less than 50-50 based on my experience) you have created a good record to continue the quest.
Write down exactly what you saw, what you did, how and when it happened, whether it happened every time or was intermittent, how you tried to correct the problem, etc. Be especially vigilant and detailed in your written description. If you used the owner's manual to trouble-shoot the problem, be sure to mention it. If you didn't, that may be the first question you have to answer when you get to the shop. It's not the question that bothers me, it's the subtle sneer from the guy asking it.
When you deliver the trailer to the service department, provide a copy of your written squawk sheet to the service manager and go over each point in detail. I try to get the technician involved in this meeting, but don't have much luck with the camper shops. It's worth a try. Also give a copy of the squawk sheet to your salesman (if applicable) and place one in the trailer (or taped to the door) for the technician. Just try to be sure that somebody else in the store has a copy of your list because the odds are pretty good that the service department will lose it, forget about it or simply ignore it.
Before you plan to pick up the trailer (or when they call to say it's ready--which they never do, you have to call to see if its ready--and it never is ready on the day promised but should be ready "sometime tomorrow or first thing the next day"
simply tell them you want to review each item on your list by phone, before you drive over to pick it up.
The usual response will be "what list?" For some reason most shops don't seem to like paperwork that they don't originate, so you can assume that the only instructions the technician received was word of mouth from the service manager "all he said was that the water pump was inop and the lower door didn't work right."
At that point you can tell the technician that the service manager and the front desk both have a copy, or fax them a copy of the original. Then and only then can you go over the real squawk list with the person who really is going to try to fix it.
Then tell the technician or the service manager to call you with the results of each item on the list before you plan to pick up the trailer. I've found that use of this procedure has caused me to spend a lot less time sitting in the waiting room or loitering in the shop/hangar waiting for my whatever to be repaired.
The bad news is that you shouldn't have to do all this stuff just to get a camper fixed. The good news is that after the first time, the shop will know you are a formidable adversary to their built-in inefficiencies and future visits will be much easier.
There's another chapter about how to work the billing side of this equation, but it's more applicable to the airplanes than the campers.