Your Gridspotter™ will need periodic cleaning.  The two places most susceptible to dirt is the threaded rod that moves the X axis, and the smooth guide rod on the back of the Gridspotter™.  Use lubricant spray silicone to clean these 2 components.  Spray a generous amount on these 2 components, until it is dripping off on them.  Then take a dry cloth and run along both the smooth guide rod and the threaded X rod while you turn the x knobs.  Repeat until clean.

When your Gridspotter™ becomes dirty, the X movement will periodically stick when you begin moving it.  This is indicative of the smooth guide rod on the back being dirty.  When the threaded X rod becomes dirty, the "X" (side to side) knobs will become harder to turn and/or there will be a louder grinding sound when they are turned.

Intuitive Corporation