The very first test i would do would to test the power supply
Load the very same test file you been using
ready everything to engrave but at the moment of pressin start, reach for the laser module and unplug its cable.
So in effect we are removing 80% of the amp load from the machine
Run the file
Granted it wont engrave a thing but will it finish all motions wihtout errors or stopping?
If this is the case, do you have an alternative 12v >3amps power adapter you could try with, this time with laser plugged in?
The fact the machine does not throw an error makes me think the controller crashes prior to error state, meaning more likely based on a power voltage drop that resets the controller. ALmost like, pressing reset button on the computer, it restarts but gives no indication why it crashed.