Hey, thanks for the vote of confidence! There's no external diagnostic that you can do. It takes a careful disassembly and attention paid to details inside. Things like slowly separating halves of the plastic shell and peering in with a flashlight to see if wires have been pulled out, careful jiggling etc. are your friend. If you have another wheel with identical parts you can swap some them out and re-test. The number one rule is change one variable at a time and re-test.