Peter, probably no point buying another bottle of wetting agent since many people use the 2 you've tried with success.(posted 8739 days ago)Maybe if you can 'hang' up the film sideways and you still get the marks, examining them closely (shape) and comparing to ones that occured when hanging the film vertically, might confirm that it is drying marks or something completely different... It's a bit of a mystery! Let us know how your test goes.