Illegal reference to private object when cooking a child level sequence with a time warp track

UATHelper: Cooking (Windows): LogSavePackage: Warning: UATHelper: Cooking (Windows): Referencers of MovieSceneTimeWarpSection /Game/ChildSequence.ChildSequence:MovieScene_0.MovieSceneTimeWarpTrack_1.MovieSceneTimeWarpSection_0: UATHelper: Cooking (Windows): LogSavePackage: Warning: MovieSceneTimeWarpTrack /Game/ChildSequence.ChildSequence:MovieScene_0.MovieSceneTimeWarpTrack_1 (2 refs) UATHelper: Cooking (Windows): LogSavePackage: Warning: 0) ObjectProperty /Script/MovieScene.MovieSceneTimeWarpTrack:Sections.Sections PackagingResults: Warning: MovieSceneTimeWarpTrack /Game/ChildSequence.ChildSequence:MovieScene_0.MovieSceneTimeWarpTrack_1 (2 refs) PackagingResults: Warning: 0) ObjectProperty /Script/MovieScene.MovieSceneTimeWarpTrack:Sections.Sections UATHelper: Cooking (Windows): LogSavePackage: Warning: 1) ObjectProperty /Script/MovieScene.MovieSceneTrackEvaluationFieldEntry:Section UATHelper: Cooking (Windows): LogSavePackage: Warning: UATHelper: Cooking (Windows): Referencers of MovieSceneTimeWarpTrack /Game/ChildSequence.ChildSequence:MovieScene_0.MovieSceneTimeWarpTrack_1: PackagingResults: Warning: 1) ObjectProperty /Script/MovieScene.MovieSceneTrackEvaluationFieldEntry:Section UATHelper: Cooking (Windows): LogSavePackage: Warning: MovieScene /Game/ChildSequence.ChildSequence:MovieScene_0 (1 refs) UATHelper: Cooking (Windows): LogSavePackage: Warning: 0) ObjectProperty /Script/MovieScene.MovieScene:Tracks.Tracks UATHelper: Cooking (Windows): LogSavePackage: Warning: UATHelper: Cooking (Windows): Referencers of MovieScene /Game/ChildSequence.ChildSequence:MovieScene_0: PackagingResults: Warning: MovieScene /Game/ChildSequence.ChildSequence:MovieScene_0 (1 refs) PackagingResults: Warning: 0) ObjectProperty /Script/MovieScene.MovieScene:Tracks.Tracks UATHelper: Cooking (Windows): LogSavePackage: Warning: LevelSequence /Game/ChildSequence.ChildSequence (1 refs) UATHelper: Cooking (Windows): LogSavePackage: Warning: 0) ObjectProperty /Script/LevelSequence.LevelSequence:MovieScene PackagingResults: Warning: LevelSequence /Game/ChildSequence.ChildSequence (1 refs) PackagingResults: Warning: 0) ObjectProperty /Script/LevelSequence.LevelSequence:MovieScene UATHelper: Cooking (Windows): LogWindows: Error: appError called: Can't save 'C:/Users/MaxChen/Documents/Unreal Projects/CookWithTimeWarp/Saved/Cooked/Windows/CookWithTimeWarp/Content/NewLevelSequence.uasset': Illegal reference to private object: 'MovieScene /Game/ChildSequence.ChildSequence:MovieScene_0' referenced by 'ChildSequence' (at '/Game/ChildSequence') in its 'MovieScene' property. UATHelper: Cooking (Windows): LogWindows: Error: begin: stack for UAT UATHelper: Cooking (Windows): LogWindows: Error: === Critical error: === UATHelper: Cooking (Windows): LogWindows: Error: UATHelper: Cooking (Windows): LogWindows: Error: Can't save 'C:/Users/MaxChen/Documents/Unreal Projects/CookWithTimeWarp/Saved/Cooked/Windows/CookWithTimeWarp/Content/NewLevelSequence.uasset': Illegal reference to private object: 'MovieScene /Game/ChildSequence.ChildSequence:MovieScene_0' referenced by 'ChildSequence' (at '/Game/ChildSequence') in its 'MovieScene' property. UATHelper: Cooking (Windows): LogWindows: Error: UATHelper: Cooking (Windows): LogWindows: Error: UATHelper: Cooking (Windows): LogWindows: Error: end: stack for UAT PackagingResults: Error: appError called: Can't save 'C:/Users/MaxChen/Documents/Unreal Projects/CookWithTimeWarp/Saved/Cooked/Windows/CookWithTimeWarp/Content/NewLevelSequence.uasset': Illegal reference to private object: 'MovieScene /Game/ChildSequence.ChildSequence:MovieScene_0' referenced by 'ChildSequence' (at '/Game/ChildSequence') in its 'MovieScene' property. PackagingResults: Error: begin: stack for UAT PackagingResults: Error: === Critical error: === PackagingResults: Error: Can't save 'C:/Users/MaxChen/Documents/Unreal Projects/CookWithTimeWarp/Saved/Cooked/Windows/CookWithTimeWarp/Content/NewLevelSequence.uasset': Illegal reference to private object: 'MovieScene /Game/ChildSequence.ChildSequence:MovieScene_0' referenced by 'ChildSequence' (at '/Game/ChildSequence') in its 'MovieScene' property. PackagingResults: Error: end: stack for UAT