disappearing outline

Curious little bug - if it is a bug and not a fault in my settings. 

Whenever I create an RGB white outline in Cdr 2019, no matter the thickness, it dissappears on zooming in or out. Even when I don't resize it, it's absent in Print Preview and nothing prints. It only happens with RGB white - every other colour is absolutely normal and it certainly doesn't occur in Cdr 2018.

I'm employing a sort of workaroundby using CMYK white if I need an outline of that colour but it's hardly satisfactory.  Any ideas?