The legs I've seen use a screw system to raise and lower the legs. There's no way for this system to drop the trailer unless the gears on the leg broke loose from the leg, and on both sides. I'd be really curious to see how this could happen. If someone knows, could they post an explanation please.
On the ones I've seen the motor drives a shaft which has bevel gears on it. The bevel gears turn a screw that does the actual raising/lowering of the legs. The screws certainly shouldn't turn without power due to the friction involved. This keeps the legs from moving even if the gears, or motor, or both, fail.
I had to change the spelling of "witch" to "which". Sorry. Lousy proofreader: me.