I had almost the same thing happen to me last night. I turned off my truck, and was listening to the end of a song (my S10 doesn't cut power to the stereo until you open the door.) I opened the door to get out for a second, and as an afterthought, I turned the volume down as it was powering down. The volume decreased, but the empeg kept playing, with my keys in hand, and the door open.

I just powered it off by the front panel, but it was strange.

-Trevor

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Mk 2, Green 12GB 080000349