Hello -
I feel like we are getting closer to solving this one for you. I appreciate your patience so far.
So I want to have you do a little bit of engine temp file pruning, to make sure that nothing is causing residual problems.
If you can please go into C:\Users[User Name]\AppData\Local\UnrealEngine\ and (making sure that all versions of Swarm, Launcher and Editor are closed) delete all subfolders. There should be at least a 4.10 directory and a Common Directory.
Next go to C:\Program Files\Epic Games\4.10\Engine\ and delete DerivedDataCache, Intermediate, and Saved Subdirectories.
Note: These directories will be rebuilt when engine first opens again, so expect a longer than normal startup time.
Now open Swarm Agent from C:\Program Files\Epic Games\4.10\Engine\Binaries\DotNET\
In Swarm Agent, Click on Cache > Clean and then Cache > Validate
Close Swarm Agent
Open Launcher and go to Library, Validate 4.10 Engine Installation.
Once Validated, open your project and attempt to build lighting again.
Thank You
Eric Ketchum