This crash was introduced in 4.14.2, and is very similar to [Link Removed], however it is still occurring in 4.14.3 (after that fix)
According to submitted crash reports, this one is not very widespread.
Repro steps currently unknown
Access violation - code c0000005 (first/second chance not available) UE4Editor_UnrealEd!TSet<TPair<unsigned int,FMeshSectionInfo>,TDefaultMapKeyFuncs<unsigned int,FMeshSectionInfo,0>,FDefaultSetAllocator>::operator=() [set.h:244] UE4Editor_UnrealEd!UnFbx::FFbxImporter::ReorderMaterialToFbxOrder() [fbxstaticmeshimport.cpp:1602] UE4Editor_UnrealEd!UFbxFactory::FactoryCreateBinary() [fbxfactory.cpp:297] UE4Editor_UnrealEd!UFactory::FactoryCreateFile() [factory.cpp:75] UE4Editor_UnrealEd!UFactory::ImportObject() [factory.cpp:150] UE4Editor_AssetTools!FAssetTools::ImportAssetsInternal() [assettools.cpp:1375] UE4Editor_AssetTools!FAssetTools::ImportAssets() [assettools.cpp:628] UE4Editor_AssetTools!FAssetTools::ImportAssets() [assettools.cpp:561] UE4Editor_ContentBrowser!SContentBrowser::ImportAsset() [scontentbrowser.cpp:790] UE4Editor_ContentBrowser!SContentBrowser::HandleImportClicked() [scontentbrowser.cpp:781] UE4Editor_ContentBrowser!TMemberFunctionCaller<SContentBrowser,FReply() [delegateinstanceinterface.h:161] UE4Editor_ContentBrowser!TTupleImpl<TIntegerSequence<unsigned int> >::ApplyAfter<TMemberFunctionCaller<SContentBrowser,FReply() [tuple.h:116] UE4Editor_ContentBrowser!TBaseSPMethodDelegateInstance<0,SContentBrowser,0,FReply __cdecl() [delegateinstancesimpl.h:318] UE4Editor_Slate!TBaseDelegate<FReply>::Execute() [delegatesignatureimpl.inl:522] UE4Editor_Slate!SButton::OnMouseButtonUp() [sbutton.cpp:275] UE4Editor_Slate!<lambda_8d0e9a1da76abd0a756a3a9d775f5ed1>::operator() [slateapplication.cpp:5010] UE4Editor_Slate!FEventRouter::Route<FReply,FEventRouter::FToLeafmostPolicy,FPointerEvent,<lambda_8d0e9a1da76abd0a756a3a9d775f5ed1> >() [slateapplication.cpp:215] UE4Editor_Slate!FSlateApplication::RoutePointerUpEvent() [slateapplication.cpp:4999] UE4Editor_Slate!FSlateApplication::ProcessMouseButtonUpEvent() [slateapplication.cpp:5462] UE4Editor_Slate!FSlateApplication::OnMouseUp() [slateapplication.cpp:5439] UE4Editor_Core!FWindowsApplication::ProcessDeferredMessage() [windowsapplication.cpp:1652] UE4Editor_Core!FWindowsApplication::DeferMessage() [windowsapplication.cpp:2071] UE4Editor_Core!FWindowsApplication::ProcessMessage() [windowsapplication.cpp:814] UE4Editor_Core!FWindowsApplication::AppWndProc() [windowsapplication.cpp:678] user32!UserCallWinProcCheckWow() user32!DispatchMessageWorker() UE4Editor_Core!FWindowsPlatformMisc::PumpMessages() [windowsplatformmisc.cpp:951] UE4Editor!FEngineLoop::Tick() [launchengineloop.cpp:2811] UE4Editor!GuardedMain() [launch.cpp:152] UE4Editor!GuardedMainWrapper() [launchwindows.cpp:126] UE4Editor!WinMain() [launchwindows.cpp:202] UE4Editor!__scrt_common_main_seh() [exe_common.inl:264] kernel32!BaseThreadInitThunk() ntdll!RtlUserThreadStart()
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-40561 in the post.