#1 - You need to service the traction control system. Similar to the engine, there are a variety of trouble codes that can pinpoint where a fault was detected. It could be a lose connection somewhere, a failed speed sensor, etc. Just from what you've posted (and probably all that you know) really doesn't narrow it down much.
#2 - Keep the contact pins and pads in the door frame clean and free of corrosion. Also keep any sliding components lubricated as needed. Other then that, there really isn't anything to do with it. From a operation perspective, I've learned to let the door do all the work. Try not to stop it midway if possible and don't open/close it rapidly. Let it open all the way.