Ok, this got me before and I didn't realize what I had done till just now. Let me see if I can explain correctly. Character #1 makes new keys (2 masters) and 3 locks. Uses the key to lock those locks, then transfers the locks and one key other to Character #2. Character #2 uses lock on the door, only to discover that his key will not open it. Character #2 then uses the key on the 2 remaining locks, and locks door #2. Door #2 opens and closes just fine. Goes back to door #1, nada. Tries to use that remaining lock on door #1 and gets "you need a master key to change locks".
So do locks not transfer? Because I could of swore people have made locks and keyed them in the past, so maybe its a random occurrence, but this is the second times happened to me.