Brak failure

If there is no pressure on the hand brake, and there is brake fluid, it would have to be a seal some where. I would guess on the slave cylinder that is located in the brake assembly on the trailer.

BTW. If this is your pig trailer what type of vehicle does the pig drive???

Wayne

Yeah. We have the same problem. Handbrake on trailer works fine in the short term but fails if left on. We always chock the wheels if on even the slightest slope while camping. Imagine the CT going ta-tas in the middle of the night, tearing the tent bit loose while you were asleep. Ouch!
The cause is corrosion in the master or slave cylinders allowing the seals to let fluid seep past and causing the pressure to be gradually released. A break overhaul should fix this but I would never trust it over time with the trailer parked on a slope.
Camper.