Building lights Crashes

Hello, as written in the title, the light build crashes with the specification below. Can anyone help to fix it? It is a map with lot of vegetation, house incl. interior and surroundings - is it because of the size of the scene? CPU and RAM should be sufficient (32GB)…

thanks
Radka

=== Lightmass crashed: ===
Assertion failed: (Index >= 0) & (Index < ArrayNum) [File:d:\build++ue4\sync\engine\source\runtime\core\public\Containers/Array.h] [Line: 611]
Array index out of bounds: 911 from an array of size 911

0x00007ffe8ece9129 KERNELBASE.dll!UnknownFunction []
0x00007ffdfa25ceaa UnrealLightmass-Core.dll!UnknownFunction []
0x00007ffdfa0c29b7 UnrealLightmass-Core.dll!UnknownFunction []
0x00007ffdfa0062b9 UnrealLightmass-Core.dll!UnknownFunction []
0x00007ff7969e0e26 UnrealLightmass.exe!Lightmass::FEmbreeGeometry::FEmbreeGeometry() []
0x00007ff7969e9822 UnrealLightmass.exe!Lightmass::FEmbreeAggregateMesh::AddMesh() []
0x00007ff796a472ed UnrealLightmass.exe!Lightmass::FStaticLightingSystem::FStaticLightingSystem() []
0x00007ff7969ef44c UnrealLightmass.exe!Lightmass::BuildStaticLighting() []
0x00007ff796a1a5dc UnrealLightmass.exe!Lightmass::LightmassMain() []
0x00007ff796a3d83a UnrealLightmass.exe!main() []
0x00007ff796ac0fcc UnrealLightmass.exe!__scrt_common_main_seh() []
0x00007ffe91f57974 KERNEL32.DLL!UnknownFunction []
0x00007ffe922aa271 ntdll.dll!UnknownFunction []