re: Electronics repair?
Bottom resistor in photo looks like it sets the speed between 6 and 8 mph
Top resistor if the lead was broken and sitting so it was just touching, it could give an intermitant opperation due to vibration etc. Its worth practicaly nothing to buy. A suitable soldering iron and solder wick/desoldering tool (solder sucker) take care not to over heat the track and use the soldering iron as a lever/scraper. Should take the famous five minuits to fix.