The issue appears to be the type of the input pin on the custom event(or function - both behave the same), under normal circumstances it should allow you to pick the enum from a list on the calling node, but in this case it does not. If you drag from the Create Literal Enum it behaves correctly
Repro Project Link: [Link Removed]
1. Create project (FirstPersonBP)
2. Create enum ([null, Default, Skill])
3. Create custom event Add Experience
4. Add the enum above as a parameter and mark it as reference
9. Call the add experience event by dragging from the execute pin of begin play
10. Create Literal enum of the Experience type and connect it to the enum input pin of Add Experience call
12. Compile and run
Result: Editor crash
Expected: Game window launches
[2018.05.01-17.06.30:777][629]LogLinux: Fatal error! 0x00007f7766e63535 FLinuxPlatformStackWalk::CaptureStackBackTrace(unsigned long long*, unsigned int, void*) 0x00007f7766d11c25 FGenericPlatformStackWalk::StackWalkAndDump(char*, unsigned long, int, void*) 0x00007f7766e14141 FLinuxCrashContext::CaptureStackTrace() 0x00007f775c63e400 CommonLinuxCrashHandler(FGenericCrashContext const&) 0x00007f7766e161cd PlatformCrashHandler(int, siginfo_t*, void*) 0x00007f7767a7a390 /lib/x86_64-linux-gnu/libpthread.so.0(+0x11390) [0x7f7767a7a390] 0x00007f7766619c8e UObject::execByteConst(UObject*, FFrame&, void*) 0x00007f7766609971 UObject::CallFunction(FFrame&, void*, UFunction*) 0x00007f776660c221 UObject::ProcessInternal(UObject*, FFrame&, void*) 0x00007f7766609f6a UObject::CallFunction(FFrame&, void*, UFunction*) 0x00007f776660c221 UObject::ProcessInternal(UObject*, FFrame&, void*) 0x00007f7766434a2e UFunction::Invoke(UObject*, FFrame&, void*) 0x00007f776661049f UObject::ProcessEvent(UFunction*, void*) 0x00007f7763558090 AActor::BeginPlay() 0x00007f776355739b AActor::DispatchBeginPlay() 0x00007f7764a141ae AWorldSettings::NotifyBeginPlay() 0x00007f7763d5315c AGameStateBase::HandleBeginPlay() 0x00007f77649fdfa9 UWorld::BeginPlay() 0x00007f7763d2ec9d UGameInstance::StartPlayInEditorGameInstance(ULocalPlayer*, FGameInstancePIEParameters const&) 0x00007f775de2f4d9 UEditorEngine::CreatePIEGameInstance(int, bool, bool, bool, bool, float) 0x00007f775de27d29 UEditorEngine::PlayInEditor(UWorld*, bool) 0x00007f775de1a1ec UEditorEngine::StartQueuedPlayMapRequest() 0x00007f775d781825 UEditorEngine::Tick(float, bool) 0x00007f775e1b31a6 UUnrealEdEngine::Tick(float, bool) 0x00000000004255f3 FEngineLoop::Tick() [/home/qa/UnrealEngine/4.19/Engine/Source/Runtime/Launch/Private/LaunchEngineLoop.cpp:3339] 0x000000000042fed3 GuardedMain(wchar_t const*) [/home/qa/UnrealEngine/4.19/Engine/Source/Runtime/Launch/Private/Launch.cpp:62] 0x00007f775c63f227 CommonLinuxMain(int, char**, int (*)(wchar_t const*)) 0x00007f775c08a830 /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf0) [0x7f775c08a830] 0x00000000004169c9 /home/qa/UnrealEngine/4.19/Engine/Binaries/Linux/UE4Editor(_start+0x29) [0x4169c9] [2018.05.01-17.06.30:785][629]LogExit: Executing StaticShutdownAfterError
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-58473 in the post.