Help! My 3 year old UPVC double glazed front door has become increasingly sticky to open and close, until this morning after I opened it I found the door wouldnt close at all - the edge of the door appears to be a fraction too wide for the frame - obviously this wasnt the case when I closed it! I had to get the door forced closed, and when opened, a tiny sliver of wood had been scrapped off the side of the door, obviously the only way it would shut. Can anyone suggest what I can do?