Questions & Answers
I was very puzzled that I couldn't get the jukebox selection buttons to bring up the correct track on my USB drive, which I had assembled on a Mac. For anyone having a similar problem, here's the issue/workaround.
Any time you mount an external drive on a Mac computer, the Mac OS automatically installs hidden files on that drive to make the drive searchable with Spotlight. These files confuse the jukebox so that your track selection buttons will not work properly. Unfortunately, even if you change your Mac settings so that it no longer uses Spotlight on that drive, the OS still writes these hidden files. So strictly speaking, the Arkrocket is not compatible with Mac-created USB content.
There is a workaround. You can still transfer music from your Mac to the USB drive, rename/renumber them as needed, etc. But before it will work correctly on your jukebox, you will need to plug the USB into a non-Mac computer (I just used an old Chromebook), select the option to show hidden files, and delete those files from the drive. After that, you should be able to use your song selection keys with no problem.
Please note that if you ever plug that USB drive back into a Mac, it's going to immediately write the problem files to it again. You can prevent this by designating the USB as "read-only" while it's plugged into the non-Mac computer. Alternately, you can just repeat the process of plugging it back into the other computer and deleting the new hidden files.
I hope this saves someone a lot of time and frustration.