Error when building lighting "Array index out of bounds: 1470 from an array of size 1458"

Confused at what I’ve done as my game has barely changed since last light build and I deleted everything new i added but still I build lighting I get this error message;

 === Lightmass crashed: ===
Assertion failed: (Index >= 0) & (Index < ArrayNum) [File:D:\Build\++UE4\Sync\Engine\Source\Runtime\Core\Public\Containers/Array.h] [Line: 674] 
Array index out of bounds: 1470 from an array of size 1458
0x00007fff8cde7c17 UnrealLightmass-Core.dll!UnknownFunction []
0x00007ff697719dd8 UnrealLightmass.exe!DispatchCheckVerify >() []
0x00007ff69765ca2c UnrealLightmass.exe!Lightmass::FEmbreeGeometry::FEmbreeGeometry() []
0x00007ff697665fbb UnrealLightmass.exe!Lightmass::FEmbreeAggregateMesh::AddMesh() []
0x00007ff6976b67b5 UnrealLightmass.exe!Lightmass::FStaticLightingSystem::FStaticLightingSystem() []
0x00007ff69766a529 UnrealLightmass.exe!Lightmass::BuildStaticLighting() []
0x00007ff6976910d7 UnrealLightmass.exe!Lightmass::LightmassMain() []
0x00007ff6976af8d3 UnrealLightmass.exe!main() []
0x00007ff697716c64 UnrealLightmass.exe!__scrt_common_main_seh() []
0x00007ff80d147034 KERNEL32.DLL!UnknownFunction []
0x00007ff80eafcec1 ntdll.dll!UnknownFunction []



0x00007ff80c3e3e49 KERNELBASE.dll!UnknownFunction []
0x00007fff8d023276 UnrealLightmass-Core.dll!UnknownFunction []
0x00007fff8d026657 UnrealLightmass-Core.dll!UnknownFunction []
0x00007fff8ce53aed UnrealLightmass-Core.dll!UnknownFunction []
0x00007fff8cde58f5 UnrealLightmass-Core.dll!UnknownFunction []
0x00007fff8cde7c50 UnrealLightmass-Core.dll!UnknownFunction []
0x00007ff697719dd8 UnrealLightmass.exe!DispatchCheckVerify >() []
0x00007ff69765ca2c UnrealLightmass.exe!Lightmass::FEmbreeGeometry::FEmbreeGeometry() []
0x00007ff697665fbb UnrealLightmass.exe!Lightmass::FEmbreeAggregateMesh::AddMesh() []
0x00007ff6976b67b5 UnrealLightmass.exe!Lightmass::FStaticLightingSystem::FStaticLightingSystem() []
0x00007ff69766a529 UnrealLightmass.exe!Lightmass::BuildStaticLighting() []
0x00007ff6976910d7 UnrealLightmass.exe!Lightmass::LightmassMain() []
0x00007ff6976af8d3 UnrealLightmass.exe!main() []
0x00007ff697716c64 UnrealLightmass.exe!__scrt_common_main_seh() []
0x00007ff80d147034 KERNEL32.DLL!UnknownFunction []
0x00007ff80eafcec1 ntdll.dll!UnknownFunction []

Hello,

We’ve made a switch to a new bug reporting method using a more structured form. Please visit the link below for more details and report the issue using the new Bug Submission Form. Feel free to continue to use this thread for community discussion around the issue.

https://epicsupport.force.com/unrealengine/s/

Thanks,

Marinna