This is normal. I experience this strange sensation with my Spark EV as well and I'll explain.
Keep in mind that the regenerative braking system is pretty unique and the braking can feel different at times. When you brake lightly, the front hydraulic brakes are not active, it is the motor that is regenerating causing the front wheels to brake. At the same time, the electronic brake modulator is activating the rear brakes hydraulically. This is allowing all 4 wheels to slow down. Half regen half hydraulic.
When you reach a certain speed, usually below 5mph, as in coming to a stop, the electric motor is not capable of effectively braking by regeneration. At this point, you will feel the braking system change how it brakes. The electronic brake modulator will transistion and deactivate regenerative braking from the motor and activate the front hydraulic brakes which is causing some people to feel the motor "disconnect". In fact, the motor never does disconnect, it's a direct drive. It is the transition from regenerative to hydraulic that is being felt. You might also notice the brake pedal is a little harder to press. You now have all 4 wheels braking hydraulically. The hydraulic system is charged by a high pressure pump that you will hear everytime you turn your Spark EV on. You'll hear a motor sound for about 10 seconds...This is the hydraulic system charging. When you turn your Spark EV off, you will hear the system make a clunk sound and hear a swoosh sound. This is the hydrualic system bleeding the high pressure charge. Also, press the brake pedal after you turn your Spark EV off and after you hear the clunk and swoosh. The brake pedal will be hard. Start the Spark EV up with your foot and you will feel it sink and soften as the hydraulic motor charges the system.
Now, another interesting characteristic I have noticed, is that if I am on the freeway and brake all of a sudden (I commute on the 405 everyday and there is a lot of slamming on the brakes in front of me) and I'm braking hard, there will be no regeneration at all. It's full hydraulic for all 4 corners. I know this is happening because if you look at the gauge cluster, the regen symbol is not spinning or is spinning, but only regenerating at 3-4KW instead of like 60kw if you are braking hard with regen. It also feels harder to brake which may feel like you lost brake boost, but you haven't. I think this is so the hydraulic system has full control of the ABS system.
Speaking of, if you activate the ABS, you will see a message pop up that says "Low Traction", indicating ABS activation in hard braking.
Just my 2 cents. There is nothing wrong with the braking system and it's just how it works based on the EV technology. It does take some getting used to, but it is what it is. Hope my explanation helps! =)
