Yes, valve adjustment done 500 miles ago. Not sure if the code started flashing before the adjustment.
Are you thinking an improper adjustment would be the problem?
Plug is an Iridium (following in your footsteps). It's 4 yrs old, wouldn't think it's the issue, unless it has vibrated loose?
But scooter starts right up and idles strong, and runs smooth and quiet for the most part.
Only thing I found on google search was faulty ignition coil (in cars, anyway).