Just got a second hand Mini and noticed that the four coloured buttons (note, inst, fx1 &fx2) are upside down.
So…
A. Is this a simple fix? How easy is it to open the case and flip them?
B. Should I be concerned that someone has needed to open the unit for some reason (someone who wasn’t very careful about how they put it back together)?
They aren’t easy to open, but you can easily flip the buttons if you have the right tools. Usually if opened you would see some signs of it around the edges of the enclosure. I dont have much experience with this or a guide so I would email support@polyend.com to help you either guide you through opening it or arrange getting it fixed for you.