this is brand new window only installed last year to our extension. it was shut since it was fitted and we I opened it this week I found the it catches from the top right corner. I have noticed that when it fully open, see picture "open position" the gape on the top left corner is bigger than the bottom one. And when I try to close it is catching at the top right corner and it need a good pull to close. see see picture "close position". I have been trying to call the guy who install it without success. what causes this distortion on the window and how it can be put right.