Ok so this weird thing just started happening with my PX-S1000.
I've got it connected via USB, into a USB hub, which then goes into my MacBook Pro.
It's playing piano sound through my computer speakers (or whatever audio output I have selected in MacOS). The piano sound is not effected by any controls on my PX-S1000... volume doesn't change anything, and the selection of Grand Piano vs Elec. Piano doesn't change the sound that's coming out. It's a mono, lo-fi piano sound and I can't get it to stop. I don't know how or when it started.
Any thoughts or ideas? I've read through as much material as I could find, and I'm at a loss.
(Not sure if this would be meant to stop it, but I have tried the Function button + C6 on/off and no change).