A few of my top hung uPVC windows that open outwards have dropped down the window frame on the opposite side from the hinges (They appear to be mounted squint to the eye as a result). This has been so drastic that the window no longer seals and lets in cold air and noise. Also the vertical seal on the same side as the hinges are mounted can let in cold air if windy. If you apply pressure you can push it out a little also. Is there any adjustments that can be made to the friction stays or is it a problem with the PVC of the window sagging or will this be fixed if the friction hinges are replaced?