When using a high sensitivity and/or flicking the screen upwards/downwards quickly, the camera can switch 180 degrees from straight up to straight down, or straight down to straight up.

Steps to reproduce

1. Increase sensitivity. In most cases default sensitivity will also suffice.
2. Move your mouse/finger upwards at a normal pace. When staring upwards, the camera will maintain at that angle (normal).
3. Move your mouse/finger upwards very quickly. Notice that the camera flickers. This is due to the camera angle flipping 180 degrees on the y-axis, going from straight up to straight down (and moving back up very quickly, making it possible for this to loop a few times).

These steps also apply downwards.

Expected results

The camera angle should maintain at 90 degrees upwards (or downwards) even when "flicking" upwards/downwards very quickly.