Protection against a circuit being closed too long or failing closed
You might be able to get away with something as simple as a PTC fuse. These increase in resistance as they warm up, and once they reach a certain point the resistance rises significantly, so that the current through them drops, but remains sufficient to keep them warm, so they remain in that state until powered down and cool off.



image from here

You'd select one that would trip after a desired time with the circuit current. If you don't know what the circuit is doing that may be less easy, it sounds like your circuit is operating a door electromagnetic lock, so that'd be easy to protect this way.