I've never noticed anything like that. The only odd behavior that I've seen from time to time is:
1) If coming to a slow and gradual stop, there is a moment when the regenerative braking will stop and apply only the traditional brakes...this would be the transition from 100% regen to 100% friction. If you are stopping with some percentage of friction, you typically will not feel the transition.
2) Sometimes, when I leave my housing tract, I will feel a very short surge in the brakes. It is at the bottom of a hill and usually I will be braking a little harder. It almost seems like it could be #1 above, but in a different scenario. It doesn't happen that often. It could even be a pothole or something that is near the stop sign.
Anyway, neither scenario seems to match your issue. If it doesn't seem like a safety issue, I'd wait till you figure out how to make it happen so you can demonstrate it to the dealer; otherwise, they won't figure it out and return it to you with no defect found (NDF).