Problem(s) Encountered:

I had just finished an exposure and was about to take some images to check the centering when the guide star jumped out of the box and the chiming started.  I believe I stopped the 
track  in Maxim-DL (i.e., stopped trying to follow the guide star), went to the  expose  tab to see what was going on, and the star had moved off the camera field -- but then I saw another
faint star drifting through, a bit slowly.  Oddly, I had to push east to correct this - the telescope had not stopped tracking, but in effect was tracking too fast!

I fussed with this a bit, and it hit on me to manually adjust the DFM telescope tracking rate to compensate - and at 14 arcsec per second, below the nominal 15.04, it was tracking well. I reacquired the correct guide star, went to restart the guider, and as soon as I started trying to follow the guide star with Maxim DL, the star started drifting again the other way -- and this time, I needed to reset the rate to the nominal 15.04 to make it work. 

This was a weird one. There doesn't seem to be anything wrong with the mechanical parts - the telescope worked nicely the rest of the night.  My best guess is that during the duration of the fault, Maxim DL was throwing the maximal westward drive correction, even though it wasn't supposed to be even sending guide signal.  The max guide rate is about an arcsecond per second of time, so it would make sense that I had to drop the guide rate from 15 to14 to get the star to stand still in the guide field.  But this is only an hypothesis, and how this happened, I have no idea.

Solution:

N/A