I purchased from the actual manufacturer on Alibaba (riding times verified supplier) . While the name is the same, they are totally denying any responsibility for support or honoring the 1-year warranty it claimed in the listing even after messaging seller they said it had a 1 year warranty for any issue 
Here is what happened:
🚲 Bike #1:
Bike randomly stalls when hitting a bump, turning corner, or going slightly off-road. It seems like a faulty sensor shuts the power off and it's very dangerous – I did, have cars behind me when the power unceremoniously shut off. The tire veered off the path due to it stalling suddenly. Unsafe and unacceptable.
🚲 Bike #2:
The Pedal Assist is inoperable. It maxes out at like 5–8 mph and doesn't work properly. I was almost stranded with a low battery, because the pedal assist will not engage.
What's worse? I contacted several times the manager assigned to me by Alibaba, who was rude, dismissive, and completely unhelpful. I contacted the company directly, and they stated, We can't help you because it is an Alibaba order - Really? You are selling the product in your name, but now you want to completely, dodge responsibility? There is no support. No replacement parts. No acknowledgement of the warranty they clearly stated in the product listing.
The bottom line is that GT73, the company behind it, is refusing to acknowledge the error in defective products, and are instead using )

Horrible experience With gt73 (Standard edition) review DONT BUY!