[Timeline] CMD+ (,) / CMD+(.) is not working to move the Timeline playhead to the previous/next keyframe.

Steps to Repro:
1. Open attached project.
2. Use the Multiple Clips scene.
3. Open Timeline window from Window > Sequencing > Timeline
4. Select the Cube object.
5. Hold CMD and press Comma (,) / Period (.), to move the Timeline Playhead to the previous/next keyframe.

Actual result:
1) Playhead does not set to the previous/next keyframe.
2) CMD + (,) opens the preference window instead of moving the playhead to previous keyframe.

Expected Result:
1) Playhead set to previous/next keyframe (seen in inlines curves or infinite tracks)
2) Shortcut conflict window should open for CMD + (,).

Environment:
Only on Mac.

Occurring with:
2019.1.0a11, 2019.1.0a10

Works on:
2019.1.0a9, 2018.3.0b12