Driving home tonight in the rain, and my wipers stopped in the middle of the screen, flicked arm up to fastest or intermittent and back to normal speed and worked again, it did this approx 6 times then was ok for the rest of the journey home, about 10 min, then when I switched them off they won't return to the bottom of the windscreen, they will stop anywhere from a few inches up to completely up at the 12oclock position, any ideas. 

sticky switch ?   (in motor/gearcase)