Bill,
Good talking with you last night. I'm fairly confident that it was just an electronic/computer-type of glitch, which while uncommon in complex electronic equipment, it does occasionally happen. I don't believe it's something you have to be concerned with at this point, but if it begins happening on a regular basis, there could be an associated problem.
The test I talked about last night works with all Yamaha PSR and Tyros series arranger keyboards. With the power turned off, hold down C2# - F2 - G2# (all three together) and while keeping them depressed, turn the power on. You will see the word "TEST" on the display. Using the Tempo +/- you can go to the test you wish to perform. The Start/Stop button starts the test. Be sure to wait for the test to complete before starting the next one.
Good Luck,
Gary
_________________________
PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)