I had this problem on my euro. I took the door trim apart and wind the windows down as much as i could. Then i sprayed some lubricants into the channels. Then i winded it all the way up and sprayed some lubricants in from the bottom. Then i kept winding it up and down a few times so the lubricant can spread along the channels. This solved the problem after around 10 times of winding up and down, the window operated as normal. Make sure you use lubricants that are suitable for rubber because some lubricants like made from wd40 can damage the rubber.