Cache keys unrentable?

[Woody]

Object 'twisty bronze key', Item type: KEY
Item is: RESTRUNG
Weight: 1, Value: 6gold, Worn in: TAKE

after renting:

Object 'twisty bronze key', Item type: UNDEFINED
Item is: RESTRUNG UNAPPROVED
Weight: 0, Value: 0gold, Worn in: TAKE

Is this as intended or bugged?

[Woody]

If it wasn't obvious in my initial post, these items no longer work as a key, and the cache mobs only pop their key once.