System Information
Operating system: Windwos 8.1
Graphics card: Nvidia gtx 1070

Blender Version
Broken:
( 2.80b beta)
( 2.80, 8839152abf5, blender2.8, 2018-12-18)

Short description of error
When using the grease pencil with an active camera view the drawing plane is not aligned to the camera(drawing plane view is selected). In some situations only by a small degree in others totaly off( like more then 60 degree difference)
Exact steps for others to reproduce the error

a rotation where it occurs(0,-180,0):
Set Camera to x:0 y:-180 and z:0 degree, press num 0, paint some strokes, num0, check

Just a thought:could this be related to viewport and camera pixel ratios differences?