Building Light complete at 0.98% !!!!

i have a problem while building light in ue4 as set my light of sun at static or movable and start building light the swarm agent stop at 0.98% or at 1 % and then it stops as it being killed or something as it was working perfect and finishes the building completely but i don’t know what happened i tried to change windows and free up spaces and nothing happens … so i hope you can help me as my project is being stopped due to this error … alt text