Hello,
I'm kinda new here (been reading for a while, but writing for the first time
)
I also made that "mistake" that everyone else appears to make: closed the shutter.
There was only one solution for me (apart from buying new lock-set): I fully disassembled the shutter part.
For this you have to take down the front cover molding, and there is a small screw on the locking mechanism on the right side if you watch from the front. After removing that screw, the shutter can be removed by rotating clockwise (if I remember well), and can further be disassembled for cleaning.
I made a mistake with that one also: the small magnets flew away, so although my shutter works now, it can be opened with any shutter-key. (but that is an information, that only I'm aware of
)