I had this type of problem. I measured the battery voltage before pressing the button and it was ok. Then I pressed the button and watched the voltage. It plays music for a couple of seconds and the voltage was ok. Then the motor kicks in and the volts drop. In my case the drop was as low as spent batteries so the train jerks and stops. I had some ALBA chinese batteries in at the time. I changed to Energizer batteries and the train now works.