Problem with button and piston

I'm a bit confused about how buttons are supposed to work.

Here's what I did:

Creative Mode as Concordia. I tried it with a previous save and also a new game.

1. Placed a large piston on the grid.

2. Set the velocity of the piston to -1

3. Placed a button on the grid.

4. Set the action of the button to 'Reverse Velocity'

5. When I click the button, the piston moves at the set velocity (-1)

6. If I click the button again, the piston moves in the opposite direction.

So far everything is working as I expect.

7. Go into the piston settings and change the velocity to -5.

8. Activate the button again, the piston moves but only at velocity 1.

When I go into the settings, the velocity of the piston has been changed from -5 back to it's previous value.

It seems as if the button is somehow remembering what the velocity is when the action is first assigned. Even if I add a second button, that button reverses the velocity at a speed of 1 and resets the piston's velocity.

What I expected was that the piston's velocity would remain as I manually set it and that the button would only reverse it.