System Information
Operating system: macOS Catalina
Graphics card: AMD FirePro D500

Blender Version
Broken: Version 2.80 (2.80 2019-07-29)
Worked: (optional)

Short description of error
I'm new to Blender, so please forgive me if this is just a user error.
I simply create a new 2D animation and draw something with a pencil, ink,... (default black color). It won't fill the stroke with the color but draw a tessellated empty area that behaves like transparent area. Color change or other settings make no difference. I have noticed that this may be a graphics card issue but I don't see any other problems... I also use other rendering software with no issues...

Has anybody encountered this problem in blender animation strokes?

Thanks, Ales

Exact steps for others to reproduce the error
Based on the default startup or an attached .blend file (as simple as possible).