That looks like a Bargman L300?? Another odd thing I found with some of them, when using the key to lock or unlock it, the inside lock would only work when the key lock was centered in its travel. That is, to lock it the key is turned counter clockwise, to unlock it the key is turned half a turn clockwise from the locked position, but to allow the inside lock to work the key has to be turned 1/4 turn from the locked or unlock position, or centered in its travel. Does this explanation make sense. Some other Uhaul
owners with the L300 have had this situation.