Liveforphysics got it right..
the product is inherently a difficult one to sell and support..
you sell a controller for a customer to install on his own motor, and possible throttle... there are so many things that can go wrong it's insane...
motor phase, and hall wires ( different brands, models, some that have been modded by users and color codes changed ) , throttle wires, ebrakes, cruise control.. all that being hooked up just takes 1 bad connection in all those wires to cause a problem.
Luckily i have a whole mountain of parts i can use to troubleshoot, and lots of experience doing it, and still find it a challenge... imagine a newb !
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A suggestion for Lyen, i'm sure he's reading this, warranty/return units could be replaced with good known units, and as dogman mentioned, returned units could be shelved until you have time to work on them, this would expedite service work and keep customers happy with a quick turn around time... hell.. charge 20$ for a swap with known to work unit and make a profit on those returns that have no problem on arrival to you..
many ways to do it, but waiting weeks for a unit with a non-working bike is frustrating and soul crushing when it's your only ride...
One of the reasons i have a collection of rides on hand, when i break one. i just ride the next in line until i fix the broken unit. lol..