We've identified two main causes of this issue;

  1. Using an Xbox 360 controller may affect freelook in cab view. Make sure that your game pad is disconnected when playing, unless you're choosing to play with an Xbox 360 controller.
  2. Using Face Tracking software can affect this, you should make sure that:
    • FaceTrackNOIR is uninstalled unless you are using it. 
    • TrackIR is disabled or not running at the time
Train Simulator does not officially support Face Tracking software and we are unable to provide you with support for this issue.