it isnīt normal. you might need to send it for a CLA. If a CLA doesn't come on handy at this time of the year with a lot of expenses and if you like to play a little with camera mechanics, you could try to see if your M2 has a first curtain adjustable brake. It could be misadjusted and stopping the first curtain too early. Most M2's only have a second curtain brake so that wouldn't work (it is adjustable from the bottom of the camera, easily accessible).
You could also give more tension to the first curtain roller, but that could most certainly spoil your speeds and besides: more tension = more noise = less smoothness = less leica feeling.
These two links can be helpful
(I am no expert, so dont trust too much on my thoughts on the subject