Tip
I have had similar issues and they even foxed the local (very good) mechanic (Ashley at Push Active, Devizes, England) until he read the small print on the sensor battery lid. Apparently this says that prior to fitting a battery, you should put it in the wrong way/upside down for a few seconds before fitting it the correct way. I guess it draws out a charge. I haven't seen the instruction myself, I am too busy enjoying the resurrected contraption to open it up and risk losing it again but I trust Ashley.