John,
I know very little about your trailer. This is from my experience. I had problems with the Arctic Fox 29-5T, and finally said, enough was enough. I rewired the brakes from the backing plate to the connection where the wiring goes inside the body to the pin box. Once I did this, all of the problems that I had with the brakes went away. Later on I found that the brake wires had been spliced in several locations. Only takes one to make things difficult or keep on set of brakes from working. I would look under the underbelly of the unit where the wiring enters. The splice for the rear brakes should be in that area.
I don't think that a dealer will get any cooperation from the manufacturer due to the time period.
That said, try it. Stranger things have happened. Since you have not used the trailer, and have found a defect that is a very serious safety concern, then IMO the dealer/manufactuer should make it right. Send emails, take a picture and you might want to get a digital infrared temperature device and get a picture of the temp of the front drums vs the rear. Keep all calls recorded and keep all emails. I would tell the dealer that since this is a safety issue, ask if there are any recalls on the trailer.
Good luck and keep us informed of what happens.
Steve & Trudy Jackson
2018 Cyclone 4005
2016 Ford F-450 6.7 PSD
AirSafe 25K hitch