I had the same problem with my 2018 Pacifica limited. In my case, the car had only been on a few minutes and I was setting a radio preset, when bam max volume. I tried resetting the infotainment settings through the settings control panel, restarting the car, nothing helped. It was basically at max volume, though I could make adjustments with the volume knob the sound was completely blown out. Turned the car off resigned that I'd have to take it to the shop. Turned it back on a few days later and the volume was back to normal. Will continue monitoring.