Bizarre firmware feeder issue

[kevin-osborn 9]

I'm posting this in case someone else runs across it. I can't reproduce it, and it may be a random fluke, but if it's not, there may be something else going on.

I have an Ultimaker 2, and I had been printing all day, When suddenly I had started a new print and the Ultimaker started singing! (stepper motor music). The brim was being put down, but when I looked in the back, the feeder was turning rapidly and continuously, grinding the filament. Thinking it was some interaction between my model, settings, and whatever I tried printing several other things from my card (exact gcode, known to work, like stretchlet) and the same behavior, power cycled, etc. no luck.

As a last resort, I reloaded the firmware (well, I guess I upgraded, since I don't know how long it's been) and all is well.

What makes me curious, is that it is a specific failure. Perhaps some internal state was reached which triggered a bug, or a very specific, non-fatal corruption occurred. (much shoulder shrugging....)