BUG:test blend file: what do happen if I apply a force to a constrained object?

I’ve a object, a cylinder, that is moved by a python script toward another object, a ball we call it the target, but I’ve also constrained the cylinder to a certain region. if the ball collides with the cylinder when it is on the limit of the region since long time the ball take a big velocity… does this happen because of some incongruence like the force increase the speed and the constraint keep the position fixed?

the blend file, http://pasteall.org/blend/769

can you also give me some suggestion?
objects look like to fly I’ve also set some constraint on z axis
please help
I need to make blender a stable simulator

I’ve verified my hypothesis, when the object is blocked by a constraints its linear velocity keep to increase this can be a bug, at least for me