Crash adding subscene to a looped subscene. Note this did not repro with brand new sequences not sure what's different about this older content.
This also occurs in Release-5.0.
Result: Crash
LoginId:6e314f9e419e0c4f57a1a7a5f28c08da EpicAccountId:7a86ba22230a43bdb5deace6a997aa49 Assertion failed: WarpCounts.Num() == NestedTransformsSize [File:D:\Builds\ReleasePrevious\Engine\Source\Runtime\MovieScene\Public\Evaluation/MovieSceneSequenceTransform.h] [Line: 443] UE4Editor_Core!AssertFailedImplV() [D:\Builds\ReleasePrevious\Engine\Source\Runtime\Core\Private\Misc\AssertionMacros.cpp:104] UE4Editor_Core!FDebug::CheckVerifyFailedImpl() [D:\Builds\ReleasePrevious\Engine\Source\Runtime\Core\Private\Misc\AssertionMacros.cpp:461] UE4Editor_MovieScene!FMovieSceneSequenceTransform::InverseFromWarp() [D:\Builds\ReleasePrevious\Engine\Source\Runtime\MovieScene\Public\Evaluation\MovieSceneSequenceTransform.h:443] UE4Editor_MovieScene!UMovieSceneCompiledDataManager::GatherTrack() [D:\Builds\ReleasePrevious\Engine\Source\Runtime\MovieScene\Private\Compilation\MovieSceneCompiledDataManager.cpp:1288] UE4Editor_MovieScene!UMovieSceneCompiledDataManager::Gather() [D:\Builds\ReleasePrevious\Engine\Source\Runtime\MovieScene\Private\Compilation\MovieSceneCompiledDataManager.cpp:858] UE4Editor_MovieScene!UMovieSceneCompiledDataManager::CompileSubSequences() [D:\Builds\ReleasePrevious\Engine\Source\Runtime\MovieScene\Private\Compilation\MovieSceneCompiledDataManager.cpp:920] UE4Editor_MovieScene!UMovieSceneCompiledDataManager::Compile() [D:\Builds\ReleasePrevious\Engine\Source\Runtime\MovieScene\Private\Compilation\MovieSceneCompiledDataManager.cpp:775] UE4Editor_MovieScene!UMovieSceneCompiledDataManager::Compile() [D:\Builds\ReleasePrevious\Engine\Source\Runtime\MovieScene\Private\Compilation\MovieSceneCompiledDataManager.cpp:686] UE4Editor_Sequencer!FSequencer::Tick() [D:\Builds\ReleasePrevious\Engine\Source\Editor\Sequencer\Private\Sequencer.cpp:673] UE4Editor_UnrealEd!FTickableEditorObject::TickObjects() [D:\Builds\ReleasePrevious\Engine\Source\Editor\UnrealEd\Public\TickableEditorObject.h:45] UE4Editor_UnrealEd!UEditorEngine::Tick() [D:\Builds\ReleasePrevious\Engine\Source\Editor\UnrealEd\Private\EditorEngine.cpp:1502] UE4Editor_UnrealEd!UUnrealEdEngine::Tick() [D:\Builds\ReleasePrevious\Engine\Source\Editor\UnrealEd\Private\UnrealEdEngine.cpp:426] UE4Editor!FEngineLoop::Tick() [D:\Builds\ReleasePrevious\Engine\Source\Runtime\Launch\Private\LaunchEngineLoop.cpp:4922] UE4Editor!GuardedMain() [D:\Builds\ReleasePrevious\Engine\Source\Runtime\Launch\Private\Launch.cpp:178] UE4Editor!GuardedMainWrapper() [D:\Builds\ReleasePrevious\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:137] UE4Editor!LaunchWindowsStartup() [D:\Builds\ReleasePrevious\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:273] UE4Editor!WinMain() [D:\Builds\ReleasePrevious\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:320] UE4Editor!__scrt_common_main_seh() [d:\a01\_work\2\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288] kernel32 ntdll
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-131206 in the post.