Luckily I purchased a warranty with the bike through the seller, Walmart, it is a Vivi brand folding ebike. I actually rode it a lot 32 miles per day back and forth to work( several thousand miles total, at the least, in the year and a half I have had it) . Good bike overall, can’t find a shop that will work on it. I pressed the insurance Co., they are refunding full purchase price, no tax included. That being said I get to keep it, I will investigate the former suggestions, to answer one scenario, I have adjusted the brakes many times, once or twice have over tightened them, just required loosening the cable then snugging it back up. (The adjuster is an Allen screw that pushes the inside pad closer on these non-hydraulic brakes). I have noticed a squeak coming from the area of the crank while riding, I will set it in the air to see what’s going on mechanically, I only have basic electrical knowledge. But have an analog multimeter. Should be able to check the voltage to the motor but that being said it works, only issue is a diminishing battery capacity as it shows on my push button controller. That may be the defect. Because even after it shows 20% left ( one out of five indicator lights lit) the batteries appear to still have a good charge, but when that last light goes out, it stops assisting.