Ok, so, to help me get a further understanding and eliminate possible issues I have a few more troubleshoots for you.
1.) If you would update your drivers for your Video card. This shouldn’t make a huge difference in builds but just to eliminate this being an issue if you would go ahead make sure you have the latest version.
2.) When building your lighting, if you would bring up your swarm agent and look through your logs to see if the swarm agent is communicating with your PC and make sure there are no errors there.
3.) I will be linking you to the swarm agent troubleshooting guide to help you decipher what exactly is going on with that and what you should expect to see vs. an issue.
4.) If you would verify your 4.9 version of UE4. From the launcher next to the label that is on your engine there is a dropdown arrow next to the Launch tab. From there click on the verify option under the dropdown. Then, if that doesn’t work, try uninstalling and reinstalling that version of the engine.
5.) Do these first just so we can cross them off the list of possible things to cause the crash. If after these troubleshoots and taking a look at your logs then we can try and move the project file you have.