Animation Window recording at frames 69, 70 and 71 does not work properly when Timeline is synced.

Yeah, this is a weird one. When you edit timeline animation clips in Animation Window, recording at frames 69-71 will create the key 1 frame back.

Steps for new project:
1. Create the objects
- Create a cube. Add an Animator component to it.
- Create a TimelineAsset asset.
- Create an gameobject with a PlayableDirector component. Link the timeline to it.
- Open Timeline Window.
- Select the timeline gameobject.
- Add an animation track.
- Bind the cube animator to the track.

2. Create the timeline clip
- Press record in timeline.
- Move the cube slightly to create a frame.
- End recording.
- Convert the track to Clip Track.
- Extend the newly created "Recorded" clip to be longer than 70 frames. 150 will do.

3. Reproduce the bug
- Double click the "Recorded" clip. That will open it in the AnimationWindow in synced mode.
- Put the time marker at 1:10 (frame 70)
- Press record.
- Move the cube slightly.
- Mouse over the AnimationWindow to refresh it.
- Observe that the key has been created at frame 69 instead of 70 as it should.

This is a bug only for frames 69, 70 and 71. It does not appear for other times. In addition to that, when used with Animation Rigging package, creating clips at those times will lock animated transforms. I can't provide reproduction details for it, since I would have to dump my whole project for it, but I thought I'd mention it. Maybe it's relevant.

I think I created a bug for it, but I can't seem to find it in the issue tracker somehow. Not sure if it went through. Anyway, seems like 1:10 is cursed. And it's screwing with our animations.

So apparently there are many more such dead zones that I've found. Specifically on frames 35, 39, 43, 50, 54, 58, 62, 63, 69, 70, 71, 99, 100, 101, 106, 107, 114, 115, 116, 122, 126. I haven't checked beyond that.

Can you please give your Timeline and Unity versions? Or file a bug with the bug reporter?
Your explanations are very clear, but I can't reproduce it here.

Either it's already fixed, or I'm missing something

Timeline 1.2.10
Unity 2020.1.3f1
I’ve updated the timeline package and seems that it’s fixed in 1.4.5.