Hello.
The “soften” brush does strange things, when I try to use it.
Here I’m using Alt+B to separate this part.
Then I turn view a little, to get to the part near the body (short stroke in the selection box and red outline).
And when I’m trying to use “soften” brush - it works as an eraser!
It happens always, when I’m viewing “through” a part which I have cut.