lighting build stops at %0 then fails for no reason

so everytime i build lights everything is good but there is a time when i build lighting it stops at %0 then its says map check found some errors but when i click on it there is only one error and it says that light maps needs rebuilt but this error were before when i was building lighting and it didnt effect anything so i dont think its from it so i tried to rebuild the light maps and clear the cache in the swarm agent but it didnt work there is no errors but it keeps telling me there is… i realy need some quick help cuz i have been working on a game for 5 months and it was time to build it and finish it Thanks!!