I have only got room for 3 speakers across the back, so upgrading from 5.1, I installed a 6th speaker. When I plugged them in, I used the right rear speaker terminals (because that made a nice neat block of cabling coming out the back). Ran the auto-setup, and it came up with an error, I couldn't get out of the error screen - had to turn the amp off and on. Moved the speaker over to the left rear terminals, everything fine. Stupid stupid stupid.