Lighting will build indefinitely in certain circumstances and can be verified in Swarm Agent that it will continue to process the maps even though the log shows it has completed. This is happening in 4.9, but works correctly in 4.8.
Users Video demonstration: [Link Removed]
1. Create a blank project.
2. In the Default Scene with the Template Floor, delete the floor mesh.
3. Build Lighting
4. Open Swarm Agent from the task bar to check status
Results: Light Build in UE4 will only display completion of 75%. Looking at Swarm Agent the process is still running indefinitely. Looking at the Logs in Swarm Agent the builder shows that it completes at 100%, but it continues to process.
Expected: Lighting will build.
Additional Repro notes:
Base test: Default scene completes at 100%
Instance 1: Lighting will hang at 75%
Instance 2: Lighting will hang at 80%
Instance 3: Lighting will complete at 100%
Head over to the existing Questions & Answers thread and let us know what's up.