i to have never had a complaint using wfp in nearly 2 years, but about 6 months ago i had a call from a regular customer saying that their dormer window was all spotty, so i said i would call back that afternoon. i went inside to look at the offending window and it was covered from top to bottom in small spots and i couldnt work out why. so i re-done the window, appoligised and left.
i really bothered me that i had a complaint and didnt know why it had happened.
next month when i returned to the house the home owner explained that it wasnt me but the window had started to break its seal and it was tiny marks inbetween the glasing so they had the unit replaced.
i was so happy and it restored my confidence . still no complaints.