WFP doesn’t do a perfect job all the time on every window over the years the complaints are down to the customer,if every job we did was checked daily we’d be in trouble there’s not many jobs that we all drive off from we can guarantee a spotless finish.
I wouldn’t worry about the odd spot you probably do leave the odd few on most jobs like I say,you just notice it more on you’re own house coz it’s looking at you lol.