I had a upvc conservatory installed 6 years ago but lately I've had problems with the door, especially on warm days. It is a hinge mounted single door with three hinges like this: Lately the door is not latching closed properly ( when just closing the door without activating the multilock). The door is hinged on the left and I'm sure if I could move it over to the right about 2mm and up 2mm it would latch ok. I have the correct allen key and can access the adjusters shown in the diagram above. The vertical adjusters are plastic (castellated?) and it will not turn at all - if I try any harder I think I'll strip the hexagon in the plastic. The horizonal adjusters turn but don't move the door at all. Could these be just seized up or am I doing something totally wrong? Any help would be appreciated.