I don't think its anything unusual. It's just that the floor acceleration is much lower than the deceleration.
When you let go of all the controls, you decelerate to a stop (at the floor deceleration rate).
When you press the opposite direction, you accelerate in the opposite direction (at the floor acceleration rate).
So yes, if you set the acceleration much lower than the deceleration, you'll get this slightly weird behavior. It doesn't seem to be a problem with the whole movement - just this specific combination of settings. Perhaps it would be more realistic, if you are changing direction, to add the deceleration and acceleration rates together. Then when you start accelerating in the direction of the arrow key you are pressing, it carries on at just the acceleration rate.