Issue was occurring with wildly varying repro steps, after speaking to Jurre and enabling gc.CollectGarbageEveryFrame 1 it was easy to conistenty reproduce this issue.
note: I was getting this issue every so often without the console command.
Fatal error!
Unhandled Exception: EXCEPTION_ACCESS_VIOLATION 0x00000078
0x0000000000000078 UnknownFunction []
0x00000000CAECD42E UE4Editor-UnrealEd.dll!UnFbx::FFbxExporter::FillExportOptions() [d:\p4\dbouimad_dev-rendering-pso\engine\source\editor\unrealed\private\fbx\fbxmainexport.cpp:155]
0x00000000CAD4BB8D UE4Editor-UnrealEd.dll!USkeletalMeshExporterFBX::ExportBinary() [d:\p4\dbouimad_dev-rendering-pso\engine\source\editor\unrealed\private\editorexporters.cpp:1863]
0x00000000CFA99250 UE4Editor-Engine.dll!UExporter::ExportToArchive() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\engine\private\unrealexporter.cpp:157]
0x00000000CFA9AA55 UE4Editor-Engine.dll!UExporter::ExportToFileEx() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\engine\private\unrealexporter.cpp:461]
0x00000000C0341024 UE4Editor-AssetTools.dll!UAssetToolsImpl::ExportAssetsInternal() [d:\p4\dbouimad_dev-rendering-pso\engine\source\developer\assettools\private\assettools.cpp:1882]
0x00000000C03415EA UE4Editor-AssetTools.dll!UAssetToolsImpl::ExportAssetsWithDialog() [d:\p4\dbouimad_dev-rendering-pso\engine\source\developer\assettools\private\assettools.cpp:713]
0x00000000BF0A0F2C UE4Editor-ContentBrowser.dll!FAssetContextMenu::ExecuteExport() [d:\p4\dbouimad_dev-rendering-pso\engine\source\editor\contentbrowser\private\assetcontextmenu.cpp:2043]
0x00000000BF09B68C UE4Editor-ContentBrowser.dll!TBaseSPMethodDelegateInstance<0,FAssetContextMenu,0,TTypeWrapper<void> __cdecl(void)>::Execute() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:327]
0x00000000BF0A2FA6 UE4Editor-ContentBrowser.dll!TBaseSPMethodDelegateInstance<0,FAssetContextMenu,0,void __cdecl(void)>::ExecuteIfSafe() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:434]
0x00000000F9147D06 UE4Editor-Slate.dll!SMenuEntryBlock::OnClicked() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\slate\private\framework\multibox\smenuentryblock.cpp:1091]
0x00000000F914E1B8 UE4Editor-Slate.dll!SMenuEntryBlock::OnMenuItemButtonClicked() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\slate\private\framework\multibox\smenuentryblock.cpp:1042]
0x00000000F90A7242 UE4Editor-Slate.dll!TMemberFunctionCaller<SMenuEntryBlock,FReply (__cdecl SMenuEntryBlock::*)(void) __ptr64>::operator()<>() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\core\public\delegates\delegateinstanceinterface.h:165]
0x00000000F90A8849 UE4Editor-Slate.dll!UE4Tuple_Private::TTupleImpl<TIntegerSequence<unsigned int> >::ApplyAfter<TMemberFunctionCaller<SMenuEntryBlock,FReply (__cdecl SMenuEntryBlock::*)(void) __ptr64> >() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\core\public\templates\tuple.h:497]
0x00000000F91242B5 UE4Editor-Slate.dll!TBaseSPMethodDelegateInstance<0,SMenuEntryBlock,0,FReply __cdecl(void)>::Execute() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:327]
0x00000000F91E2477 UE4Editor-Slate.dll!TBaseDelegate<FReply>::Execute() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\core\public\delegates\delegatesignatureimpl.inl:537]
0x00000000F920F3D4 UE4Editor-Slate.dll!SButton::OnMouseButtonUp() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\slate\private\widgets\input\sbutton.cpp:282]
0x00000000F91502CD UE4Editor-Slate.dll!SMenuEntryButton::OnMouseButtonUp() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\slate\private\framework\multibox\smenuentryblock.cpp:439]
0x00000000F9025F4C UE4Editor-Slate.dll!<lambda_1002768c627006711ef2f351a87ec0e7>::operator()() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5254]
0x00000000F8FF8095 UE4Editor-Slate.dll!FEventRouter::Route<FReply,FEventRouter::FToLeafmostPolicy,FPointerEvent,<lambda_1002768c627006711ef2f351a87ec0e7> >() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:234]
0x00000000F9092792 UE4Editor-Slate.dll!FSlateApplication::RoutePointerUpEvent() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5243]
0x00000000F907AF92 UE4Editor-Slate.dll!FSlateApplication::ProcessMouseButtonUpEvent() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5745]
0x00000000F906D7A2 UE4Editor-Slate.dll!FSlateApplication::OnMouseUp() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5725]
0x00000000172BE40B UE4Editor-ApplicationCore.dll!FWindowsApplication::ProcessDeferredMessage() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:1725]
0x00000000172B1A28 UE4Editor-ApplicationCore.dll!FWindowsApplication::DeferMessage() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:2171]
0x00000000172C02AC UE4Editor-ApplicationCore.dll!FWindowsApplication::ProcessMessage() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:888]
0x00000000172AD589 UE4Editor-ApplicationCore.dll!FWindowsApplication::AppWndProc() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:725]
0x0000000040EA1C24 USER32.dll!UnknownFunction []
0x0000000040EA156C USER32.dll!UnknownFunction []
0x00000000172C13D6 UE4Editor-ApplicationCore.dll!FWindowsPlatformApplicationMisc::PumpMessages() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\applicationcore\private\windows\windowsplatformapplicationmisc.cpp:129]
0x00000000075150C8 UE4Editor.exe!FEngineLoop::Tick() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\launch\private\launchengineloop.cpp:3219]
0x0000000007525430 UE4Editor.exe!GuardedMain() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\launch\private\launch.cpp:166]
0x00000000075254AA UE4Editor.exe!GuardedMainWrapper() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\launch\private\windows\launchwindows.cpp:134]
0x0000000007532389 UE4Editor.exe!WinMain() [d:\p4\dbouimad_dev-rendering-pso\engine\source\runtime\launch\private\windows\launchwindows.cpp:210]
0x0000000007533D67 UE4Editor.exe!__scrt_common_main_seh() [f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:253]
0x0000000041108364 KERNEL32.DLL!UnknownFunction []
0x00000000438D7091 ntdll.dll!UnknownFunction []
0x00000000438D7091 ntdll.dll!UnknownFunction []
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-50128 in the post.