Disclaimer, I literally know nothing of the function of locks other than to secure things to -hopefully- another score thing so as to prevent theft.
that being said, I have a hard time believing that the mechanism the key slides into wasnt affixed to metal internals of the lock.
maybe the plastic shroud limits how deep you can slide the key in and in that way, the ramps or bumps on the key dont line up correctly with the lines or tumblers inside the lock preventing it from working as intended?