I had 3 Upvc re-enforced replacement windows put in just over a year ago and now have one glass unit which has cracked on the inside (lengthways top left corner arced to bottom left corner) and have also just noticed a crack in the frame on another of the windows ( bottom part of the frame) it runs parallel with the seam between the two units of glass (hope that makes sense!) Can anyone tell me why this might of happened, if a cracked frame can be fixed and if the fitters could be at fault. Thanks in advance for any replies.