To be safe, jack it up and take your hubs off and inspect the brake shoes, pivot points and wiring to the magnet actuator. With all that heat you could have melted a wire connection and its grounding out or fused up your pivot points which will need lub to free them up. Check your brake pads as well depending on previous use they may be worn down and need replacing. They may have been glazed by the heat as well making them useless. With any brake issues it's best to take them apart and see what damage occurred, you have a heavy 38 footer good brakes are a necessity!! I guess what I'm saying is there's no short cut fixes, take it apart and have a look.