Strange behavior when painting mesh details on terrain

I am getting very buggy behavior when painting mesh detail objects on terrain. Sometimes it paints OK, sometimes it only draws in certain square "tiles", or painting flowers will erase previous grass, or deleting will make it reappear in nearby places.

for instance, in the pic below I try to paint the whole area but some sections appear to be unpaintable:


Is there maybe some configuration I am missing, or some limitations to this kind of detail objects?

when I use 2D grass it works fine.

I doubt it's related, but I'll mention just in case that I often have editor errors (for a long time now) like "Unsupported type vector" or "Failed to create object Undo, because it is too large".

 

Solved, needed to reduce the detail resolution per patch on my terrain