Windscreen misting problems?

[6EXO]

Hi
I know this is a stupid question but having tried everything but the problem keeps coming back”!
Hopefully I will be able to save sometime when I go to my dealer with a already diagnosed answer”! Like a problem I had before with the car where I was able to go in to my local BMW Dealer and pin point the problem to them Thanks to your guys here in this forum”!

Here goes”!
It all started a few weeks ago when for no apparent reason my windscreen misting up leaving a hazy (slightly greasy) film after a couple days, at first I thought it could be that it needs a good clean but I have taken in to a local car wash had windows cleaned and with in 2 or 3 days the problem is there again”! It’s annoying because even dough I press the de-mister button to clear, it still leaves that hazy film on”!
This only happens on the windscreen”!!!
Regards