I literally have the same amp with the same problem as a result from doing the same thing. I bought mine used on reverb though, so I can't just return it.
I successfully updated the firmware (all versions), which didn't work unfortunately. Now I'm just waiting to hear back from the help desk ticket I submitted last week. So I am awaiting a response for that.
I was so happy with this amp. It's hard to believe there's a flaw like this and no way to do a hard factory update outside of the software.
I figured I would reply here to try and grease this squeaky wheel to get a fix for it.