Why did I not have front wheels spinning?

[Hummie2]

You may be getting some wear in the shift detent cams or between the encoder motor and the shaft that turns the cams. That would cause the shift forks not to reach their full range of travel. The encoder motor reaches it's proper position and sends the signal to indicate the shift was complete, but wear in the cams,forks,shaft etc. may cause some lost motion in the shifting mechanism causing the lock sleeve not to be fully locked or unlocked completely.

If the problem happen again its time to open the t-case up and see what's going on in there.