Electrical Gremlins

Several years ago I rewired my Triumph Bonneville. This included new electronic ignition plus a new modern charging system. Since lock down my battery has been discharging itself and after doing some checks it turned out to be the regulator/ rectifier was at fault ,and it was taking the battery power to earth. I have put the older system back in place and the battery is receiving a heathy charge. What caused this fault is a mystery to me.