Array index out of bounds: 17098 from
an array of size 17098
I’m not sure, but 17000 objects in level is a big number.
How many RAM do you have?
i had this error when i built the lighting,
=== Lightmass crashed: ===
Assertion failed: (Index >= 0) & (Index < ArrayNum) [File:d:\build++ue4+release-4.18+compile\sync\engine\source\runtime\core\public\Containers/Array.h] [Line: 610]
Array index out of bounds: 17098 from an array of size 17098
0x00000000AA6A9D98 KERNELBASE.dll!UnknownFunction []
0x0000000063E65E54 UnrealLightmass-ApplicationCore.dll!UnknownFunction []
0x00000000587E1A8B UnrealLightmass-Core.dll!UnknownFunction []
0x0000000058772E98 UnrealLightmass-Core.dll!UnknownFunction []
0x000000006164EFB6 UnrealLightmass.exe!UnknownFunction []
0x000000006165E054 UnrealLightmass.exe!UnknownFunction []
0x0000000061653B8B UnrealLightmass.exe!UnknownFunction []
0x00000000616658A4 UnrealLightmass.exe!UnknownFunction []
0x000000006169D863 UnrealLightmass.exe!UnknownFunction []
0x00000000616C04DA UnrealLightmass.exe!UnknownFunction []
0x000000006171EC25 UnrealLightmass.exe!UnknownFunction []
0x00000000AB1D2774 KERNEL32.DLL!UnknownFunction []
0x00000000ADAF0D51 ntdll.dll!UnknownFunction []
0x00000000ADAF0D51 ntdll.dll!UnknownFunction []
what cause this ???
im using light mass importance volume
i have hp z800 PC, 32 RAM, 12 CORE 2.9 intel processor, 2GB GPU (NIVIDIA 4000), Win10
i had this problem before i just reinstalled the windows and the engine still the same error
can someone please help my im ding here 
thank you
My ram is 32 GB, do you think upgrading to higher RAM will solve this ?
I think this error caused by some out-of-memory process in Lightmass. 32 GB ram looks enough. Try to decrease number of objects in level. Or split it on few streaming levels and build light for each level separately.
I deleted everything thing abd tried building with one box only still the same error, but when I open a new project every thing is smooth and good, maybe I should switch to cryengen or unity , im just sat I wasted a month bulding this project. Thank you very much for your reply:)
I deleted everything thing abd tried building with one box only still the same error, but when I open a new project every thing is smooth and good, maybe I should switch to cryengen or unity , im just sat I wasted a month bulding this project. Thank you very much for your reply:)
Can you please tell me how to do this?
Try to delete swarm cache files.
In swarm agent open Cache → clean
I had the same issue, but only with 350 objects in my scene and this solved my problem, THANKS A LOT