I have created a new brush group.
I have set up my brush and changed the mode to Darken and saved the brush in my new group.
If I am using a general brush and change to my new brush preset, everything works but if I change back to a general brush, the brush mode still stays at darken and not normal.
Any suggestions please
The previous standard brushes don't have the code bytes for these properties.
They don't know anything about "mode" or "color" and they weren't converted by Adobe's engineers to meet the new functionality.
Suggestion? None - except you want to save them all as new brushes.