Corel Painter 2019 some weird real watercolor brushes Mac issue issue

Hi, 

Either on : 

 Macpro 5.1 4 core  XEON 2,93 GHZ GPU RADEON 580 Go

or MacBook Pro I7 4 core 2,3 ghz Bi GPU intero iris pro / Nvidia GT 750 

"esquisse aquarelle réaliste" (in french) 12 BRUSH IN REAL WATERCOLOR 

show circles when applying (pink color)

On Mac Pro, same gear, bootcamp windows 10,

the brush is acting well. (beige)

On the Mac side, same with newer tryout version of painter,

either with Nvidia or AMDcard.

If anyone could please test it on Mac with previous system to find out if this is a Catalina issue ?