My 1.8t has the 2 following issues. When I press the buttons to do the windows up the drivers side goes up then goes down again 1/3rd of the way from top. So press up again and it does it again. Eventually it doesn't. It does on the odd occasion. 2nd issue I noticed today the revs drop to around 5.5-6 and back to 8. It does this now or then. I have had new spark plugs, oil change, air filter and fuel filter. What can cause this? No errors on vcds.