Brakes grabbing

Could be an intermittent ground issue. Either ground to the vehicle or individual wheel magnet grounds.
Simple solution to just get you on the road, first try turning the gain all the way down although I don’t really think that will work.
If it doesn’t, disconnect the power wire to the brakes, at the trailer plug or junction box on the tongue and drive carefully.

Make sure that your break a way switch has not been pulled out.

Get your bearings repacked ASAP after you figure out the cause. We had a stuck brake coming down a hill where we couldn't stop. Got it corrected and looked for a shop that could repack the bearings, almost made it but had a blowout 40 miles short. If you can't find a shop very near to you I'd try to find a mobile tech to do it. Btw it doesn't have to be an RV shop, we eventually got ours done by a tire shop that does big rigs as they had high bay doors, trailer shops that handle boat or commercial trailers are also an option.

What kind of trailer? What kind of brakes? Can’t help much without any info.

^Agree more info, year of trailer also. Often times a trailer with lots of use/miles, can have brake wires shorting inside the axle, due to worn wire insulation.

Jerry

MFL wrote:
^Agree more info, year of trailer also. Often times a trailer with lots of use/miles, can have brake wires shorting inside the axle, due to worn wire insulation.

Jerry

Can you explain how "wires shorting inside the axle" can cause a brake to grab?

Hey JR, this is a common issue, but normally takes at least a light touch of pedal, that can result with braking similar to pulling the pin. Very aggressive, tires chirp/maybe smoke. As Grit mentioned, turning the gain way down will help, but braking will be diminished.

It starts mostly intermittent, due to the wiring moving/bouncing inside the tube.

Quick fix..cut the wires going through tube, and run new cross wire outside the tube.

MFL wrote:
Hey JR, this is a common issue, but normally takes at least a light touch of pedal, that can result with braking similar to pulling the pin. Very aggressive, tires chirp/maybe smoke. As Grit mentioned, turning the gain way down will help, but braking will be diminished.

It starts mostly intermittent, due to the wiring moving/bouncing inside the tube.

Quick fix..cut the wires going through tube, and run new cross wire outside the tube.

Sorry, I do not have enough info to tell the OP what the problem is. But what I can say is unless a cut and run more wires "tech" has really screwed up already the problem is NOT a short in the axle. Unless something is wrong elsewhere, the only time current flows in/out of axle is when break-way or controller signals apply the brakes. Now there can be a short 2 ways; brake wire to axle. The magnet does not get power/shoes don't move to drum/brake does not work. Or brake wire to ground wire. The magnet does not get power/shoes don't move to drum/brake does not work.
The 3rd, and most common issue is a broken wire (brake or ground) in that case the magnet does not get power/shoes don't move to drum/brake does not work.
As the OP is not saying the brakes are failing to apply, the issue is not wires in axle

If I was tasked with fixing I would first ask if any trailer lights on. I suspect that the issue is the brake wire is getting power from someplace it should not, most likely in the plug.

Check brake light switch.

Sound like something in intermittently applying your brakes. Do you by chance use your left foot on the brake pedal? I've seen people burn up their brake pads because they rest their left foot on the pedal.

Check that the emergency brake cable and pin is not pulled.

Find a mobile RV tech to come pull the wheels and inspect the brakes to make sure nothing is broken.

as said earlier, turn the gain way down on the controller or snip the brake wire between the 7 pin and the axle. Then drive carefully to an RV shop to get it repaired.