ATM Laser Collimation /Focuser Question

["Al Klayton" <aklayton@pcisys.net>]

When using a laser collimator in a 1.25" JMI Crayford focuser on my 8" Dob I
observe the following: If I start with the focuser racked all the way out,
and then slowly rack it all the way in while observing the laser beam on the
primary mirror, the beam moves first in one direction .... and then wanders
BACK even though the focuser tube is still moving in. Although the degree of
beam movement is fairly small, about + - 3/8 inch or so (the beam stays
within the donut ring used to mark the center of the mirror), I wonder if
this is normal? Seems to me that even if the laser collimator is slightly
out of collimation itself, or if the JMI focuser is not perfectly square to
the OTA, or the secondary mirror is not adjusted perfectly, I would still
not expect the wandering back and forth type movement of the beam -- I'd
expect beam movement in one direction only since the focuser tube is only
moving in one direction. I conclude the wandering motion reflects
imperfection in the movement of the JMI focuser tube ( I've tried adjusting
the focuser).  If this type of situation was normal, then the accuracy of
the laser collimation method would depend on the position of the focuser
tube, which can't be right.
Am I being to critical -- do others see this type of beam movement?
Or...what?
Thanks,
Al