Hook bolts not retracting enough

Hi. When I depress my handle, the two hook bolts don't go in far enough, only by about 3mm, but enough to stop the door opening. You have to put all you body weight down on the handle to get that last 'click' to open the door. Its now getting to the point that my wife and kids cannot open the door of it has been locked. Any advice?...
It is an Anglian composite front door with Winkhaus lock, 2 hook bolts and a thumbturn.

 

Showing signs of internal wear within the gearbox, check your guarantee as it may cover this

 

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