That is odd indeed. LightBurn folks will need to pitch in here I think.
I did encounter this older thread. Doesn’t sound quite the same situation as you as downgrading didn’t change the behavior. Turned out to be a NIC issue in this case. There might be some troubleshooting methods you could try:
Just updated new lightburn, now not able to send to laser - LightBurn Software - LightBurn Software Forum