legacy animation destroyed my project timeline, animations no longer work

unity 2017 1.3

my project was going perfectly until unity said this:

'The AnimationClip 'idle' used by the Animation component 'Rat_AI' must be marked as Legacy.'

so, i made that particular animation a legacy and my timeline stopped working - all animations from all characters - even after i changed it back to generic and even deleted it

even on my backups, none of my animation works - so far, i've lost an entire project that's shipping for christmas

i can open new scenes and the timeline animations work - just not my project timeline - now, i get

PlayableAsset returned a null Playable on Instantiate
UnityEngine.GUIUtilityrocessEvent(Int32, IntPtr)

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ArgumentNullException: Argument cannot be null.
Parameter name: The playable passed as an argument is null. Call IsValid() on playables to verify that they are valid before you use them.
UnityEngine.Playables.PlayableHandle.SetPlayStateInternal (UnityEngine.Playables.PlayableHandle& playable, PlayState playState) (at C:/buildslave/unity/build/artifacts/generated/common/runtime/PlayableBindings.gen.cs:242)
UnityEngine.Playables.PlayableHandle.SetPlayState (PlayState value) (at C:/buildslave/unity/build/artifacts/generated/common/runtime/PlayableBindings.gen.cs:143)
UnityEngine.Playables.PlayableExtensions.SetPlayState[Playable] (Playable playable, PlayState value) (at C:/buildslave/unity/build/Runtime/Export/Director/PlayableExtensions.cs:28)
UnityEngine.Timeline.ScheduleRuntimeClip.Create (UnityEngine.Timeline.TimelineClip clip, Playable clipPlayable, Playable parentMixer, Double startDelay, Double finishTail) (at C:/buildslave/unity/build/Extensions/Timeline/Runtime/ScheduleRuntimeClip.cs:57)
UnityEngine.Timeline.ScheduleRuntimeClip..ctor (UnityEngine.Timeline.TimelineClip clip, Playable clipPlayable, Playable parentMixer, Double startDelay, Double finishTail) (at C:/buildslave/unity/build/Extensions/Timeline/Runtime/ScheduleRuntimeClip.cs:45)
UnityEngine.Timeline.AudioTrack.OnCreatePlayableGraph (PlayableGraph graph, UnityEngine.GameObject go, UnityEngine.IntervalTree tree) (at C:/buildslave/unity/build/Extensions/Timeline/Runtime/Audio/AudioTrack.cs:49)
UnityEngine.Timeline.TrackAsset.CreatePlayableGraph (PlayableGraph graph, UnityEngine.GameObject go, UnityEngine.IntervalTree tree) (at C:/buildslave/unity/build/Extensions/Timeline/Runtime/TrackAsset.cs:308)
UnityEngine.Timeline.TimelinePlayable.CreatePlayableGraph (PlayableGraph graph, UnityEngine.Timeline.TrackAsset asset, UnityEngine.GameObject go, UnityEngine.IntervalTree tree) (at C:/buildslave/unity/build/Extensions/Timeline/Runtime/TimelinePlayable.cs:194)
UnityEngine.Timeline.TimelinePlayable.CreateTrackPlayable (PlayableGraph graph, Playable timelinePlayable, UnityEngine.Timeline.TrackAsset track, UnityEngine.GameObject go, Boolean createOutputs) (at C:/buildslave/unity/build/Extensions/Timeline/Runtime/TimelinePlayable.cs:211)
UnityEngine.Timeline.TimelinePlayable.CompileTrackList (PlayableGraph graph, Playable timelinePlayable, IEnumerable`1 tracks, UnityEngine.GameObject go, Boolean createOutputs) (at C:/buildslave/unity/build/Extensions/Timeline/Runtime/TimelinePlayable.cs:150)
UnityEngine.Timeline.TimelinePlayable.Compile (PlayableGraph graph, Playable timelinePlayable, IList`1 tracks, UnityEngine.GameObject go, Boolean autoRebalance, Boolean createOutputs) (at C:/buildslave/unity/build/Extensions/Timeline/Runtime/TimelinePlayable.cs:129)
UnityEngine.Timeline.TimelinePlayable.Create (PlayableGraph graph, IList`1 tracks, UnityEngine.GameObject go, Boolean autoRebalance, Boolean createOutputs) (at C:/buildslave/unity/build/Extensions/Timeline/Runtime/TimelinePlayable.cs:106)
UnityEngine.Timeline.TimelineAsset.CreatePlayable (PlayableGraph graph, UnityEngine.GameObject go) (at C:/buildslave/unity/build/Extensions/Timeline/Runtime/TimelineAsset.cs:268)
UnityEngine.Playables.PlayableAsset.Internal_CreatePlayable (UnityEngine.Playables.PlayableAsset asset, PlayableGraph graph, UnityEngine.GameObject go, IntPtr ptr) (at C:/buildslave/unity/build/Runtime/Export/Director/PlayableAsset.cs:54)
UnityEngine.GUIUtilityrocessEvent(Int32, IntPtr)

 

all my other playables for the project work fine - it's just the one main scene that no longer works - i only changed the animation because unity prompted me to do so and i've lost a month of work/frame-by-frame animation, if i can't fix that playable asset

 

i messed around with it and it's playing again - i don' know what i did - i tried everything, even other instances of unity, etc. - i used older playables for awhile then, my main playable started working again - go figure...

 

My project also have with this problem, and it was later found out. because one Audio Track's "Audio Playable Asset Clip" is null in timeline




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ArgumentNullException: Argument cannot be null.
Parameter name: The playable passed as an argument is null. Call IsValid() on playables to verify that they are valid before you use them.
UnityEngine.Playables.PlayableHandle.SetPlayStateInternal (UnityEngine.Playables.PlayableHandle& playable, PlayState playState) (at C:/buildslave/unity/build/artifacts/generated/common/runtime/PlayableBindings.gen.cs:242)
UnityEngine.Playables.PlayableHandle.SetPlayState (PlayState value) (at C:/buildslave/unity/build/artifacts/generated/common/runtime/PlayableBindings.gen.cs:143)
UnityEngine.Playables.PlayableExtensions.SetPlayState[Playable] (Playable playable, PlayState value) (at C:/buildslave/unity/build/Runtime/Export/Director/PlayableExtensions.cs:28)
UnityEngine.Timeline.ScheduleRuntimeClip.Create (UnityEngine.Timeline.TimelineClip clip, Playable clipPlayable, Playable parentMixer, Double startDelay, Double finishTail) (at C:/buildslave/unity/build/Extensions/Timeline/Runtime/Evaluation/ScheduleRuntimeClip.cs:55)
UnityEngine.Timeline.ScheduleRuntimeClip..ctor (UnityEngine.Timeline.TimelineClip clip, Playable clipPlayable, Playable parentMixer, Double startDelay, Double finishTail) (at C:/buildslave/unity/build/Extensions/Timeline/Runtime/Evaluation/ScheduleRuntimeClip.cs:43)
UnityEngine.Timeline.AudioTrack.OnCreatePlayableGraph (PlayableGraph graph, UnityEngine.GameObject go, UnityEngine.IntervalTree`1 tree) (at C:/buildslave/unity/build/Extensions/Timeline/Runtime/Audio/AudioTrack.cs:48)
UnityEngine.Timeline.TrackAsset.CreatePlayableGraph (PlayableGraph graph, UnityEngine.GameObject go, UnityEngine.IntervalTree`1 tree) (at C:/buildslave/unity/build/Extensions/Timeline/Runtime/TrackAsset.cs:297)
UnityEngine.Timeline.TimelinePlayable.CreatePlayableGraph (PlayableGraph graph, UnityEngine.Timeline.TrackAsset asset, UnityEngine.GameObject go, UnityEngine.IntervalTree`1 tree) (at C:/buildslave/unity/build/Extensions/Timeline/Runtime/TimelinePlayable.cs:201)
UnityEngine.Timeline.TimelinePlayable.CreateTrackPlayable (PlayableGraph graph, Playable timelinePlayable, UnityEngine.Timeline.TrackAsset track, UnityEngine.GameObject go, Boolean createOutputs) (at C:/buildslave/unity/build/Extensions/Timeline/Runtime/TimelinePlayable.cs:218)
UnityEngine.Timeline.TimelinePlayable.CompileTrackList (PlayableGraph graph, Playable timelinePlayable, IEnumerable`1 tracks, UnityEngine.GameObject go, Boolean createOutputs) (at C:/buildslave/unity/build/Extensions/Timeline/Runtime/TimelinePlayable.cs:157)
UnityEngine.Timeline.TimelinePlayable.Compile (PlayableGraph graph, Playable timelinePlayable, IEnumerable`1 tracks, UnityEngine.GameObject go, Boolean autoRebalance, Boolean createOutputs) (at C:/buildslave/unity/build/Extensions/Timeline/Runtime/TimelinePlayable.cs:106)
UnityEngine.Timeline.TimelinePlayable.Create (PlayableGraph graph, IEnumerable`1 tracks, UnityEngine.GameObject go, Boolean autoRebalance, Boolean createOutputs) (at C:/buildslave/unity/build/Extensions/Timeline/Runtime/TimelinePlayable.cs:85)
UnityEngine.Timeline.TimelineAsset.CreatePlayable (PlayableGraph graph, UnityEngine.GameObject go) (at C:/buildslave/unity/build/Extensions/Timeline/Runtime/TimelineAsset.cs:220)
UnityEngine.Playables.PlayableAsset.Internal_CreatePlayable (UnityEngine.Playables.PlayableAsset asset, PlayableGraph graph, UnityEngine.GameObject go, IntPtr ptr) (at C:/buildslave/unity/build/Runtime/Export/Director/PlayableAsset.cs:54)
UnityEngine.GUIUtilityrocessEvent(Int32, IntPtr)