I have the new RadKick Belt Drive and have been experiencing a drop in power under 50% charge. No matter how hard I pedal when the battery is below 50% I cannot get the speed to 20mph. Generally it just feels sluggish at lower battery levels. Under 20% I started getting the ERROR 6 message - Battery undervoltage error with a complete loss of power. I love the bike, but very frustrating to see a drop in power especially on longer rides. Anyone else having this experience?