Quote from Paul on July 4, 2019, 11:32 am

Intermittent issue seen by us that we first could not identify.

The issue was that the controller just stops in the middle of a job. The root cause was actually the installed air pump that caused electro magnetic interference. Best is to eliminate all possible combinations and deduct the culprit. Try to engrave without a running laser and air pump and see whether it  persists or not until you find the root cause. Hope this helps!