Intermittent Fault with LB and Legacy Gerbil

Hi,
I am having an intermittent fault with my gerbil powered K40 and lightburn. When processing a job the laser will sometimes stop and not carry on. No errors are reported in LB or the gerbil console. Only fix is to stop the job and reset the device. It then works again. But the fault seems intermittent so hard to track down. It seems to always during engraving tasks.
Not sure if it’s hardware or software related.
I am using the older avr powered gerbil with GBRL drivers and Linux. generally they work well apart although there is also a slight issue that when the job finishes LO remains pulled to ground meaning the laser is still enabled.
Any help would be much appreciated
Cheers Bob