Here is a good writeup on a similar popup with surge brakes and the fix from the Popup Explorer website.
I posted here before about problems I had with my Jayco surge brakes. In a nutshell, whenever I towed - no matter how hilly or flat the terrain was - my axles would heat up to the point that they were *very* hot, sometimes you could smell grease burning, and the brakes would lock up and skid the trailer whenever they applied themselves. I had them checked and fixed / adjusted 3 different times, had the master cylinder replaced, and even took out almost all the cargo out of the trailer (thinking it was overloaded), but the problem still persisted.
I was to the point of thinking I had a trailer that I couldn't use, and I was losing confidence in my ability to tow it reliably. In fact, I was considering trading the thing in for a hybrid or TT (gasp!), since I couldn't find another pop-up brand or model that I wanted to buy.
In a last ditch effort to fix the problem, I took the trailer to a custom TRAILER shop (not an RV repair place) that unbeknownst to me was about 15 minutes from my home. They do it all - I saw many, many custom builds on their lot, and the owner told me they were fabricated from the ground up. And they had experience working on any type of trailer imaginable. I saw trailers for pulling dragsters and racing boats, horse trailers, a hot dog trailer that the owner pulled to fairs, and a couple of big toy haulers on their lot.
Bottom line is that the owner told me that surge brakes are a very inferior design and should not be used on any type of trailer except boat trailers. The problem - which is what I experienced - is that the very design of the surge brake system promotes over application of the brakes even when the TV isn't braking and the parts on the trailer just can't handle it. That's especially true on hilly terrain - you might use your engine in the TV for breaking, but the surge brakes are constantly applied by the trailer due to inertia. You could even experience this going down a level street. Overapplication of the brakes heats them up, and as we all know, hot brakes fail..
The owner of the trailer shop suggested that I completely rip out the surge break system and replace it with electric brakes, which is exactly what I did. He did an immaculate job and the problem was completely solved. I've towed my trailer 3 times since the conversion - one was a repeat of the worst tow I had ever done with any PUP - a STEEP and multi-level decent and accent through a canyon - and the brakes worked flawlessly. The hubs were barely warm when I pulled over to check them. In a nutshell, I've got my trailer back!
So my advice for Jayco owners having brake problems is to dump the surge brake system. Mine was a big headache. I even noticed that newer Jayco models don't use them anymore; they've converted to using electric brakes as well.
The only downside was the cost - about $950 bucks by the time he was done. I've got a dual axle PUP so the fact that it needed two sets of everything certainly added to cost. But I got my camper (which was in like new condition when I bought it) for $5k less than it cost new (I found the signed paper work in the PUP) and about $1500 to $2000 less than I've seen used ones advertised for, so I guess I'm breaking even.