This seems very much like an intermittent communications problem trashing the file in transit. When the LightBurn file has not changed, but the resulting file in the machine is different, there’s data damage in between.
Assuming the Mac is connected to the laser through a USB link, these (sometimes lengthy) discussions may be relevant:
If any of that applies, the least awful way out seems to be using the machine’s Ethernet connection, rather than USB. The router must be set up to avoid assigning the machine’s fixed IP address to another device through DHCP, because two devices at the same IP address cause bizarre problems.