Problem(s) Encountered:

The classic nodding problem returned while I was tracking a target around 2 hr west and a bit north of the horizon.  It manifests as random north-south jerks of about 10-15 arcsec; in this case it always returned to the center position (it was not guided back -- the guider recenters things much more

slowly than what I saw.  The nodding occurred intermittently and whole minutes went by without it.

Solutions:

Wind perhaps?  I hope...