Cannot sample RT then draw that material back into RT?

Trying to accomplish MAX blending when drawing to render target, but it does not work as i expected. Why is material acting like it samples clear render target? If i draw resulting render target to another render target and sample it in material instead instead, it works fine.

While there is a way to read from and write to the same render target, this won’t work in blueprints and you need to make sure that you do not read from the target, you are writing to.