Using a Thumbdrive. As soon as it gets above around 75 degrees outside it starts jumping around. The song will skip to a different section and back and then it will switch songs. Sometimes it will also jump to AM or FM stations and hop around there. Dealer just shrugs his shoulders. Last fall during final service before winter they said they could fix it by updating the firmware. Wasn't able to test it until this past month and it's not fixed. Driving me batty!