Controller not working as expected or is it a bug?

[heikone]

At first, thanks for repo! A very practical piece of software for HA.
I've tried it out and generally the controller is available in my HA, but I have problems with understanding the results of it.

My scenario is:
I want to control an actor, which can be set from -10...+10 to compensate a reading from -5...+5 to a set point of 0.
When the reading is below 0, the controller shall move to positive values.
In principle, I'm talking about a temperature room controller, which shall bring a temperature difference between measured and actual temperature to 0 by opening a valve from -10...+10.

This my initial setup:

I'm expecting the controller to be 0 points and not -10, because set point is reached.

Another example:

Setting sensor value to -5 did not change anything, but I've expected the controller to become greater than 0 points.

Last example:

Sensor value is +5 and the controller only changed from -10 to -9.

I can't explain the behavior of the controller in the context of my example!
Maybe somebody can advise help?