lightmass crashed

i was working on a game and everytime i build lighting it was fine but this time when i tried to build lighting it showed me this:
i tried to clear the cache in the swarm agent but it still didnt work…
i rly need some help!! Thanks!

It looks like it’s crashing due to very large amounts of foliage

No i Fixed The Foliage Problem And The LightMass Still Crashes