Hi you will probably have three locking keeps on the frame.On each plate there should be some adjustment to move part of the keep either side by about 5mm.this can be done with either loosening a couple of screws on the keep slide keep over towards the outside of the door and retightening the screws or there will be an allen key screw head you can turn with an allen key to move the keep over towards the out side of the door again.By doing this when you close the door and lift handle the shoot bolts/hooks will be more compressed when entering the locking keeps.Sounds complicated but shouldnt be to difficult!Hope this helps.
Markg
February 2010