My trailer has one of them fancy battery operated locks... During the inspection the tech was proud to show me how it worked... easy peezy
Got home and loaded all our stuff and locked it up... came back a week later to put a few more items in the trailer... fancy door lock didn't work... okay no big deal, just change the batteries.. Next weekend... you guessed it... Took the batteries out and two and a 1/2 years later I still ain't replaced them...