stuttering while vertical take-off with brakes on

I noticed yesterday (it was my first flight and I was unaware about the fact that there are breaks because of the wheels :music_whistling:) that the Mi-8 begins to stutter in the vertical axis while taking-off with brakes still activated.

It feels as if something hits every two seconds on top of the H/C to push it down.

I suppose that's a bug (the brakes aren't connected to the mainrotor, aren't they? ;-) )

I don't have the module (yet), but is it the tires skipping on the ground as the struts extend on takeoff?