To reproduce:

1. Download attached project "TimelineBugRepro2018_UpgradedFrom2017.zip" and open in Unity 2017.4.11f1
2. Open "ActualScene" scene
3. Enter Play mode
4. Press "Q" or "W" on your keyboard and observe how Virtual Camera moves
5. Exit Play mode
6. Build and Run project in Standalone
7. Press "Q" or "W" on your keyboard and observe how Virtual Camera moves - it will move like in Unity Unity Editor
8. Close Built project
9. Close Unity Editor
10. Open the same project in Unity 2018.*
11. Open "ActualScene" scene
12. Enter Play mode
13. Press "Q" or "W" on your keyboard and observe how Virtual Camera moves - moves will differ
14. Exit Play mode
15. Build and Run project in Standalone
16. Press "Q" or "W" on your keyboard and observe how Virtual Camera moves - it will move like in Unity 2017.4.11f1
17. Close Built project
18. Select the "Main Camera" in Hierarchy and in Inspector window set Cinemachine Virtual Camera (Script) Priority to 9 or lower than 10
19. Enter Play mode
20. Press "Q" or "W" on your keyboard and observe how Virtual Camera moves - it will move like in Unity 2017.4.11f1 and Standalone

Notes:
- This issue appears only on Windows and Unity Editor
- On OSX and Standalone, everything works as expected
- Recreating the same project on Unity 2018.* from the scratch fixes this issue

Reproduced on Unity 2018.1.0b5, 2018.1.9f1, 2018.2.9f1 and 2018.3.0b3
Could not reproduce on Unity 2017.4.11f1, 2019.1.0a1 and 2019.1.0a2
Could not check for correct regression version on Unity 2018.1.0b4 and lower because changing Cinemachine Virtual Camera (Script) Priority does not fix the problem and in Standalone Camera behavior will be the same as in Unity Editor