I've done windows
twice - especially those downstairs - when I'm "in the zone".
Just not thinking and on autopilot. Even done the side of a non-customer neighbour's "square" bay which was very close - from the garden of my custy!
I've missed windows by accident too. Got an angry answer phone message a couple of winters ago from a guy with a big extended old farmhouse where I did all the windows but missed the two downstairs on the gable end (I did the ones above them, go figure) and one of these was the kitchen side window in front of the sink. (Schoolboy error!)
He told me he didn't appreciate me putting a slip through and not cleaning his windows.
I phoned him back and it turned out I'd missed two out of about twenty and a conservatory. Just went back and did them in the morning and he apologised for accusing me of doing none. Shook hands and that was it - back in love again!