loopnmore

I purshased a used JM4 Looper and today I did the first tests with it. The JM4 restarts every time I want to check the tracks on the SD card. I think, the card is empty. Whenever I turn the control wheel (the one right next to the display), the JM4 restarts after a few moments. The logo appears on the display and I hear the typical crackling sound in the headphones. Is this a firmware error? Does anyone know this? I haven't found anything like this on the Internet.