Why is terrain smoothing not working?

I am extremely frustrated with this. I am just trying to sculpt the geometry for my terrain, but I can't make anything look natural because I can't smooth it properly.
What am I doing wrong?

I can set the brush opacity up high and all the other tools will make a dramatic effect with just a single click. I have to push the opacity down to the lowest possible setting and it still provides crazy results that require using the most gentle and calculated strokes.
But yet when I use the smooth height tool I have to set the opacity clear to the highest possible setting and nothing changes. Every bump in my terrain stays as a bump. Every dip stays as a dip. Nothing changes.

What am I doing wrong? What do I need to do to get this tool to shape my topography?

 

I also have this problem in a number of projects. Why can't i smooth my terrains when all the other terrain sculpting tools work?! This is a critical tool and a google search revewals that this issue has been happening for years. In my current project i have multiple terrains. On one terrain the smooth tool works normally, on other terrains it does nothing. Can someone from unity even acknowledge this and tell me how to fix it asap

 

In the exact same situation here. Surprised there isn't an obvious solution to it by now.