Magickwoods Black Glass Vessel Sink "install quarter" Questions

We have just had our brand new Franke KBV 651 sink installed. However we are having prblems with the quarter turn plug. This no longer works. We have taken it apart and the plastic bayonet (lugs) seam

...turn at a time. Check for leaks and turn again if needed. Tell your hubby it's ok...I don't like installing those sinks either...always afraid they'll break and that the customer is gonna take my ...