In patch PTR 1.4, the camera does not work properly when adding to the current rotation value. The only instance of "glitching" is at the -90° angle. Once the rotation hits this angle or passes it, regardless of velocity or value change, it will cause the camera to momentarily stop in it's track, reset at exactly -90° and continue onwards. It is highly annoying, especially in WASD type movement settings for FPS/TPS cameras.
NOTE: Please note that it only glitches when ADDING to the current rotation value and not subtracting. It works perfectly fine when subtracting.