Prerequisites to reproduce:
1. Open Regional Settings
2. Go to Formats tab
3. Set format to Russian (Russia)

Steps to reproduce:
1. Create a new Unity project (or open the user-submitted one)
2. Set the .NET Scripting Runtime Version to 4.6 (if starting off a new project)
3. Import Cinemachine (if starting off a new project)
4. Create a timeline on an empty game object
5. Create a Cube, set its position to (1, 0, 0) (IMPORTANT! Everything seems to work correctly with the position set to (0, 0, 0))
6. Drag the Cube onto the timeline created in #4. Select to create a new Animation Track
7. Press the Record button
8. Try to move the Cube along the X-axis
9. Observe the error and failure to record that keyframe

Note: see the user-submitted reproduction video in the comments if any of the steps is not clear

Expected result: timeline does not break and the object's movements are recorded
Actual result: timeline appears to be broken and the object's movements do not register (it also throws a FormatException error)

Reproduced with: 2017.1.5f1, 2017.4.9f1, 2018.2.0f2, 2018.3.0a7