FPS Camera dead zone

[ofrm1]

Probably a simple fix, but for some reason the FPS camera cannot turn 360 degrees for me. There's always a dead zone where the camera just acts like it runs up against a wall and won't go any further. It's incredibly frustrating when you're playing on a map with mountains and you can't move the camera in view of your units that are behind a hill or mountain because of this dead zone.

Is this working as intended, or is there a setting I can change to allow full movement?

Thanks

[Silentwings]

Which game/engine/etc....?