Reproduction steps(GIF attached):
1. Open the attached "Archive" project.
2. Select the "New Animation" in the project view.
3. Open the Animation window (Window > Animation).
4. Expand the Scale property.
5. Click on the Scale.x input box.
6. Click Tab on the keyboard.

Actual behavior:
Pointer moves into the frame input bar.

Expected behavior:
Pointer moves into the Scale.y input bar.

Reproduced in: