No clue what exactly the issue is but it doesn’t even work with the mutable sample and the current source build (tried 5.7.3 before that).
I tried to package with a CustomizableObjectPopulation and it just won’t
Assertion failed: ClassWeights[i].Class->CustomizableObject->IsCompiled() [File:C:\UnrealEngine\Engine\Plugins\Experimental\MutablePopulation\Source\CustomizableObjectPopulation\Private\MuCOP\CustomizableObjectPopulation.cpp] [Line: 95]
0x00007ffeee4fa5a8 UnrealEditor-Core.dll!FDebug::CheckVerifyFailedImpl2() [C:\UnrealEngine\Engine\Source\Runtime\Core\Private\Misc\AssertionMacros.cpp:745]
0x00007ffe97850ed8 UnrealEditor-CustomizableObjectPopulation.dll!UCustomizableObjectPopulation::BeginCacheForCookedPlatformData() [C:\UnrealEngine\Engine\Plugins\Experimental\MutablePopulation\Source\CustomizableObjectPopulation\Private\MuCOP\CustomizableObjectPopulation.cpp:95]
0x00007ffee9f28cdc UnrealEditor-UnrealEd.dll!UCookOnTheFlyServer::RouteBeginCacheForCookedPlatformData() [C:\UnrealEngine\Engine\Source\Editor\UnrealEd\Private\CookOnTheFlyServer.cpp:12611]
0x00007ffee9eefed1 UnrealEditor-UnrealEd.dll!UCookOnTheFlyServer::CallBeginCacheOnObjects() [C:\UnrealEngine\Engine\Source\Editor\UnrealEd\Private\CookOnTheFlyServer.cpp:4448]
0x00007ffee9f1e2e1 UnrealEditor-UnrealEd.dll!UCookOnTheFlyServer::PrepareSaveInternal() [C:\UnrealEngine\Engine\Source\Editor\UnrealEd\Private\CookOnTheFlyServer.cpp:4201]
0x00007ffee9f1db12 UnrealEditor-UnrealEd.dll!UCookOnTheFlyServer::PrepareSave() [C:\UnrealEngine\Engine\Source\Editor\UnrealEd\Private\CookOnTheFlyServer.cpp:4109]
0x00007ffee9f229f4 UnrealEditor-UnrealEd.dll!UCookOnTheFlyServer::PumpRuntimeSaves() [C:\UnrealEngine\Engine\Source\Editor\UnrealEd\Private\CookOnTheFlyServer.cpp:5119]
0x00007ffee9f30b5a UnrealEditor-UnrealEd.dll!UCookOnTheFlyServer::TickMainCookLoop() [C:\UnrealEngine\Engine\Source\Editor\UnrealEd\Private\CookOnTheFlyServer.cpp:1575]
0x00007ffee9f30154 UnrealEditor-UnrealEd.dll!UCookOnTheFlyServer::TickCookByTheBook() [C:\UnrealEngine\Engine\Source\Editor\UnrealEd\Private\CookOnTheFlyServer.cpp:1422]
0x00007ffee8d381ed UnrealEditor-UnrealEd.dll!UCookCommandlet::RunCookByTheBookCook() [C:\UnrealEngine\Engine\Source\Editor\UnrealEd\Private\Commandlets\CookCommandlet.cpp:607]
0x00007ffee8cfd35a UnrealEditor-UnrealEd.dll!UCookCommandlet::CookByTheBook() [C:\UnrealEngine\Engine\Source\Editor\UnrealEd\Private\Commandlets\CookCommandlet.cpp:559]
0x00007ffee8d1d7f3 UnrealEditor-UnrealEd.dll!UCookCommandlet::Main() [C:\UnrealEngine\Engine\Source\Editor\UnrealEd\Private\Commandlets\CookCommandlet.cpp:278]
0x00007ff73bd2a5d1 UnrealEditor-Cmd.exe!FEngineLoop::PreInitPostStartupScreen() [C:\UnrealEngine\Engine\Source\Runtime\Launch\Private\LaunchEngineLoop.cpp:4053]
0x00007ff73bd20a1b UnrealEditor-Cmd.exe!GuardedMain() [C:\UnrealEngine\Engine\Source\Runtime\Launch\Private\Launch.cpp:146]
0x00007ff73bd20d0a UnrealEditor-Cmd.exe!GuardedMainWrapper() [C:\UnrealEngine\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:123]
0x00007ff73bd24590 UnrealEditor-Cmd.exe!LaunchWindowsStartup() [C:\UnrealEngine\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:277]
0x00007ff73bd35be4 UnrealEditor-Cmd.exe!WinMain() [C:\UnrealEngine\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:334]
0x00007ff73bd382f6 UnrealEditor-Cmd.exe!__scrt_common_main_seh() [D:\a_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288]
0x00007ff824fce8d7 KERNEL32.DLL!UnknownFunction