Need help with Lighting issue (Lightmass failing)

Hey everyone

My scene isn’t complicated at all, and the lighting I’m trying to pull off is literally just two rectangle lights in a confined space.

These are the errors I’m getting:

<None> === Lightmass crashed: ===
Assertion failed: Importer.ImportData((FBaseMaterialData*)this) [File:D:/Build/++UE4/Sync/Engine/Source/Programs/UnrealLightmass/Private/ImportExport/Material.cpp] [Line: 13]

0x00007ff83be3a839 KERNELBASE.dll!UnknownFunction ]
0x00007fffbee1faa7 UnrealLightmass-Core.dll!UnknownFunction ]
0x00007fffbee224b1 UnrealLightmass-Core.dll!UnknownFunction ]
0x00007fffbecab22a UnrealLightmass-Core.dll!UnknownFunction ]
0x00007fffbec0ce87 UnrealLightmass-Core.dll!UnknownFunction ]
0x00007fffbec0d540 UnrealLightmass-Core.dll!UnknownFunction ]
0x00007ff691042f0a UnrealLightmass.exe!Lightmass::FMaterial::Import() ]
0x00007ff6910143cb UnrealLightmass.exe!Lightmass::FLightmassImporter::ConditionalImportObjectWithKey<Lightmass::FMaterial,TMap<Lightmass::FSHAHash,Lightmass::FMaterial * __ptr64,FDefaultSetAllocator,TDefaultMapHashableKeyFuncs<Lightmass::FSHAHash,Lightmass::FMaterial * __ptr64,0> >,Lightmass::FSHAHash>() ]
0x00007ff69104666c UnrealLightmass.exe!Lightmass::FStaticLightingMesh::Import() ]
0x00007ff6910a49a1 UnrealLightmass.exe!Lightmass::FStaticMeshStaticLightingMesh::Import() ]
0x00007ff691019795 UnrealLightmass.exe!Lightmass::FLightmassImporter::ImportObjectArray<Lightmass::FStaticMeshStaticLightingMesh,TMap<FGuid,Lightmass::FStaticMeshStaticLightingMesh * __ptr64,FDefaultSetAllocator,TDefaultMapHashableKeyFuncs<FGuid,Lightmass::FStaticMeshStaticLightingMesh * __ptr64,0> > >() ]
0x00007ff6910448be UnrealLightmass.exe!Lightmass::FScene::Import() ]
0x00007ff69102aa84 UnrealLightmass.exe!Lightmass::BuildStaticLighting() ]
0x00007ff69104e11d UnrealLightmass.exe!Lightmass::LightmassMain() ]
0x00007ff69106cb1a UnrealLightmass.exe!main() ]
0x00007ff6910d5cfc UnrealLightmass.exe!__scrt_common_main_seh() ]
0x00007ff83c447bd4 KERNEL32.DLL!UnknownFunction ]
0x00007ff83e3eced1 ntdll.dll!UnknownFunction ]

This is taken directly from my message log, not sure how to fix. I’ve added a lightmass importance volume because that was an issue that popped up before, but even then it’s still failing to build lighting.
Any help will be greatly appreciated.

Hello, can you send screenshot of your scene? And also, are you using GPU or CPU? Kernel Base crash is pretty common on gpu users. Try clearing and revalidating your Swarm Agent.