1. Open the attached "TimelineBug" project and "Repro" scene
2. Select Cube prefab in Hierarchy, if you are using Default Editor layout, make sure that Timeline and Scene windows would be visible
3. Enter playmode
4. Play the track in the Timeline window and observe Cube moving
5. Press M key to mute the track

Expected result: Since Track is muted, Cube stops moving
Actual result: Track is muted, but Cube still moves

Notes:
1. Issue only happens in playmode and is reproducible with both Mute and UnMute properties
2. If the track is muted/unmuted before playing it, Mute/UnMute properties seems to work okay

Reproduced with - 2017.2.0a4, 2017.1.0b10, 2017.1.0b1