I made the mistake of leaving on the handbrake on my trailer for a couple of weeks, to stop it rolling down a short slope in my allotted parking place. When I tried to move off on my return home today, the brake on one side had seized and the wheel made an impressive skid mark. I vaguely remembered reading something about unseizing it by going in reverse. It worked, and with a very loud bang.
The trailer seems none the worse for this experience but will be going in for a service, which is probably long overdue. I won’t be using the handbrake again except for short bursts and in future will rely on chocks to banish runaway trailer misery.