How old is "original" Sondors? A decade? More?
Every bike controller I've bought has had garbage for main electrolytic capacitors. Ie if I unplugged it from the battery, let it sit a minute, then plugged it back in, there would be a big spark. Charge leaked away in 1 minute. None of my ebike systems were from majors like Bosch or Shimano.
I upgraded this garbage by replacing the main caps, 470 uf @ 50 v, with industrial caps rated for service life of >3000 hours. No spark after a couple of minutes unplugged. At 10 years all the little e-caps would be suspect, too. The good parts cost ~150% of the price of the garbage 500 hours caps at retail. Ecaps have a + label near one pin, or a minus in balls label near the other pin.
I buy such caps from newark or digikey. Don't buy at a local electronics parts store, I got nothing but garbage grade from them before the debit card was invented and newark allowed individuals to purchase from them. Similar garbage e-caps are installed in consumer grade electronic devices of all types. The HDTV converters from ***-Mart, a year. *-Mart, 2 years. Stellar HDTV converters fail after ~ 5 years. Legend, Element, Vizio no-name flat screen TV's, 18 months. LG or Samsung, 5 years. Professional PA amps & mixers from Peavey, Crown, QSC, 15 years operated 24/7.