iOS fast-forwards through all tracks & doesn't play any

Strange to hear / watch this happen:

Hit "Play" and nothing comes through the headphones (or speakers) at all; check the display and it's just zooming through all the tracks, spending less than a second before going to the next, over and over.

Mucked about for awhile and then came up with a theory:

It's due to the "Sound Check" feature, which I had just turned back on - and it now has to scan every single track to know what to do before it plays any.

Great background here: http://productionadvice.co.uk/sound-check-album-mode/

Sure enough, as soon as I let it go through all of them, it was able to play.

And then I turned "Sound Check" back off. :)