Twitch in power expander

We have a twitch (they run for a second, randomly) in the motors connected to the power expander when the cortex is off. Any ideas?

We have been just unplugging the battery to the expander when we turn off the cortex, but it is a bother.

one second as in “one-missisipii…”
or more like a few mini-secs?
the minisec twitch is normal in vex
but i’m not sure about the one full second “twitch”
and you should still always unplug the power expander battery from the micro controller because it will leech the battery power
(you might find your batteries dead Monday mornings)
other than that, i couldn’t think of anything…