Well, here goes, on finishing the build it didn't work, batteries are good, no loose connections so change MCU......

MCU changed & jumps forward on start-up & flashes red, that's all it will do so then change power board....

Great, everything works except head motor travels at light speed in both directions with a thump so order a replacement head motor......

Head motor replaced & low & behold, doesn't work at all on the batpack but on plugging in AC charger, head motor works as it should but no "chirp" & just flashes pinkish, anyone else had this cascade of problems, will strip again & test batbox connections but cannot see that is the problem as all I have done is change head motor, not impressed