You asked if anyone else has experienced a problem like yours. I have had brake problems with all my travel trailers and my current fifth wheel, everything from forgetting to plug in the trailer pig tail to the truck, to broken wires under the trailer.
With my current fifth wheel, I've had brake failure 4 times now. The first 2 was caused by the trailer brake relay in the truck failed. When that happened (both times) we were miles and miles from no where and had to tow with no trailer brakes.
Another time, I simply forgot to plug in the pig tail. Unfortunately, the plug for the pig tail drug the ground and disolved into shreds. I could not plug it into the truck. I had to tow home with no lights or brakes on the trailer.
The last time was about a year ago. We were on our way from Indiana to Louisiana. We just pulled out of a campground where we spent an overnight and I felt the brakes were not responding in the trailer. I drove about 15 miles on the interstate and pulled into a truck stop / gas station. I crawled under the trailer and examined both sets of wires. On the passenger side, I found a wire broken. The rubber insulation on the wire was rubbed completely off and the bare wire must have bent and moved around enough in the wind, it finally broke in two. It was an easy fix, I simply spliced it back together and taped it up real good. Brakes worked wonderful after that.
That incident made me realize I had a rubbing exposed wire for some time, I just did not know it, because sometimes the brakes in the trailer seemed real squirrely and other times were perfectly fine. I think the wire got thinner and thinner as it rubbed, until it finally broke.
My "saving grace" for my brake failures is the fact I drive a one ton dually diesel 3500 long bed, crew cab pick-up truck. It's heavy, it's long, and it's got POWER. But ... It also has the stopping capacity to brake for the trailer (if and when) the trailer brakes fail. I did have a couple white knuckle events happen when the trailer brakes were out, and I did skid the truck tires attempting a quick stop and the trailer kept pushing forward. Still, the truck maintained control of the trailer, even without trailer brakes. I think THAT is why I drive a one-ton dually. I know (IF) the trailer brakes fail, the truck is still capable of stopping a 14,000 pound anchor on wheels behind me.
So yes..... I have had similar problems with brake wires breaking in two.