UE4.26 - Foliage tool creates duplicates on top, why?

I guess this is a new bug in Unreal, It has been happening since I started working with UE4.26, after I finish adding foliage with the foliage tool, I find that it has been adding double the amount of instances, one on top of the other, I discovered this because my scene lost too many FPS at certain locations, so I started deleting instances and after grabbing and moving one of them I found another exact one underneath, with the exact size, like, if my instances where created twice at the same spot.

This are my painting settings:

foliage tool set

This is a big problem, bacause I canot delete every instance manually, my only way to fix this is to delete the entire foliage and paint again… scared, that in the end, duplicates will appear again.

Just imagine populating the scene with 1,00,000 grass meshes, and then figure out that underneath of every instance, there is another one… and they are impossible to find, because they are exactly the same one, even same size, even do I use a random scale between 2 and 3 and they are located at the exact spot, because the foliage tool painted 2 exact instances instead of 1, and there is not any option, to avoid 1 foliage to sit on top of the other.