ArgumentException error when moving keyframe in Animation Window

Repro:
1- Open project in attachment.
2- Select animation clip 'idle' in project browser.
3- Open Animation Window.
4- Select any master keyframe in the dopesheet and drag it.

You should see the following error in the console:
ArgumentException: An item with the same key has already been added. Key: -1568898133
System.Collections.Generic.Dictionary`2[TKey,TValue].TryInsert (TKey key, TValue value, System.Collections.Generic.InsertionBehavior behavior) (at <ac823e2bb42b41bda67924a45a0173c3>:0)

Reproducible: 2018.3.3f1, 2018.2.16f1, 2018.1.1f1, 2017.4.19f1