This is not a regression. This also occurs dating back to 4.15 and 4.14.
The editor crashes on this check in FLevelEditorActionCallbacks::Paste_CanExecute() when updating the Edit menu state:
check(GEditor->GetSelectedActorCount() == 1);
GEditor->GetSelectedActorCount() is 2
Mac:
Expected Result: the sphere component is added back the the stairs mesh
Actual Result: the editor crashes on the redo
Windows:
Expected Result: the Edit menu should open
Actual Result: the editor crashes on opening the Edit Menu
[2017.05.30-19.22.52:252][398]LogMac: === Critical error: === SIGSEGV: invalid attempt to access memory at address 0x3 [2017.05.30-19.22.52:252][398]LogMac: FGenericPlatformMisc::RaiseException(unsigned int) Address = 0x277c62b (filename not found) [in UE4Editor-Core.dylib] FOutputDeviceMacError::Serialize(wchar_t const*, ELogVerbosity::Type, FName const&) Address = 0x2977f8f (filename not found) [in UE4Editor-Core.dylib] FOutputDevice::Logf(wchar_t const*, ...) Address = 0x2a58a9d (filename not found) [in UE4Editor-Core.dylib] FDebug::AssertFailed(char const*, char const*, int, wchar_t const*, ...) Address = 0x29bed0e (filename not found) [in UE4Editor-Core.dylib] FLevelEditorActionCallbacks::Paste_CanExecute() Address = 0x1d0233f2 (filename not found) [in UE4Editor-LevelEditor.dylib] FUICommandList::CanExecuteAction(TSharedRef<FUICommandInfo const, (ESPMode)0>) const Address = 0x8cc744f (filename not found) [in UE4Editor-Slate.dylib] FSlateMacMenu::IsMenuItemEnabled(TSharedRef<FMenuEntryBlock const, (ESPMode)0> const&) Address = 0x8da1d28 (filename not found) [in UE4Editor-Slate.dylib] FSlateMacMenu::UpdateCachedState() Address = 0x8d9ef11 (filename not found) [in UE4Editor-Slate.dylib] FMacPlatformMisc::PumpMessages(bool) Address = 0x293cb79 (filename not found) [in UE4Editor-Core.dylib] FEngineLoop::Tick() Address = 0x2685b7b (filename not found) [in UE4Editor] GuardedMain(wchar_t const*) Address = 0x268de12 (filename not found) [in UE4Editor] -[UE4AppDelegate runGameThread:] Address = 0x269c01a (filename not found) [in UE4Editor] -[FCocoaGameThread main] Address = 0x2934136 (filename not found) [in UE4Editor-Core.dylib] __NSThread__start__() Address = 0xae30bbcd (filename not found) [in Foundation] _pthread_body() Address = 0xc268b9af (filename not found) [in libsystem_pthread.dylib] _pthread_body() Address = 0xc268b8fb (filename not found) [in libsystem_pthread.dylib] thread_start() Address = 0xc268b101 (filename not found) [in libsystem_pthread.dylib]
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-45529 in the post.