March 26, 2016 at 3:17 pm #22435
Which model of EggBot is it (other than old)?
It is possible that the jerky movement is due to the motor current setting. When energized, the pen arm should be moveable with gentle pressure, but should not “fall over”. If it is too hard to move (which could cause jerkiness) then you may want to turn it down a little.
Otherwise, try a slower movement setting, to see if it can perform well at a lower speed.