Hey , while building lights for a level this error might pop-up and the light build stops.Have tried most of the methods defined for clearing this error like building the UnrealLightmass.sln from ue4 source.Need to find concrete method to resolve this issue.
All the steps below would be recommended if nothing else on the other answerhub threads is helping you.
The only way this error was resolved for me was by doing the following steps (hack):
- On light build got Lightning Build Failed. Swarm Failed to Kick off error
2)create a separate new level
3)put some random assets ,lights and light build
4)Once done open the previous level which gave the error
5)Select all assets in game and press delete - then select (no to all) option - Try build again
Hope it helps .
Regards