scenic door/window problem

Our 55 reg Grand Scenic was recently bumped on the driver's side door whilst parked (thankyou to the *** that drove away!). I've managed to suck out most of the dent, but the window only winds down halfway now. I've removed the door card and can see that the glass and yellow plastic thingy is hitting a large black plastic part that sits between the window and the outer door skin. If I push this piece towards the door skin, the window will then wind down but it still scrapes on this black plastic part. I can't see what function this black plastic has and I wonder how I get it to move more towards the outer skin? I can't see that the remaining very small dent could be stopping it moving out of the way. Could it be removed without harming anything? Any advice much appreciated!