I've just moved into a house with uPVC windows, and I've noticed a couple of them have the same problem.
They are all of the type with the bottom of the window swinging out to open, with the 'hinged' edge being the top of the window, (although the actual hinges are on the side edges of the window).
I hope that makes sense!
Anyway, as I close the window it seems to be coming into the frame nicely, and then as the bottom of the window comes inot the frame so as I can lower the handle and fasten the latch, the top edge of the window seems to kick-out, leaving a gap between the top of the window and the frame.
Is there anything I can do with this? I didn't know if perhaps there is usually some adjustment on the hinges?
This is on an upper floor window, so until I can get hold of a long ladder I can't actually inspect the hinges themselves.