Related to case 996934

Steps to reproduce :

Create a Timeline asset and add an Animation Track and Animation Clip
Create a Game Object in the scene and add the timeline asset
Select the Animation Clip and put a non-zero value for ease-in
Move the playhead to the middle of the Animation Clip
Right Click -> Editing -> Split (or click S)
See that both the clips have the original ease-in value instead of just the one on the left