I'm having an issue with my Gigabyke Groove electric bike ( 750w 48v 14h) has total shutdown after hitting little over 10 mph. I have to disconnect and reconnect battery cable to get it to restart. I've checked the battery voltage and it shows 46v. I also have some issues from time to time that when I turn the bike on it speeds up suddenly, without me touching the throttle. Yeah not good.. any advice would greatly be appreciated. Thanks