This issue is unfortunately still not fixed in the new update version 3.3.0.1391.
It's very disapointing.
I can add, that when the slope is in center position, then it's the same level as when the sustain level is in the center position. But if sustain gets more level than that, then it's more than the slope level ever can get. So the slope level simply need more power from the center position and up.