I've had a few months experience with wfp and by and large it's going well.However I'm still,fairly regularly,getting these white spot marks in the top corners of windows.This is despite making sure the frame has been properly scrubbed and left to stop dripping and with plenty of rinsing.It's happening too often and I'm getting baffled.It's defeating the object a bit if I have to stick around until they dry off and then wipe the spots away with a cloth.Any ideas would be appreciated.