The issue with "jumps" was caused by the X-Y stepper motor spindle pulley set screw coming loose, thus, allowing the pulley to "slip" around on the motor shaft during a print session. A simple fix was to remove the set screw, realign the pulley to the motor spindle flat spot, and apply some lock tight to the set screw, and re-tighten. Have not see any issues since it was fixed.

Mike