I have two Swifty Liberte folding ebikes and one has stopped working with electric assistance, after some checks and finally swapping the control boxes I have established that it’s a control box failure. The box in question is by Santroll Electric Automobile Technology, Model No B-WZKD3613KA-JM102-F4, I have emailed the company mentioned and also the bike manufacturer and am yet to receive a reply. I have also contacted Amazon who were the original supplier of this model ebike, nothing , they don’t carry spares. Any suggestions please