Take-off altitude not followed by Z setpoint in Mission mode

Hi all,

While climbing to the set waypoint altitude after take-off, the Z setpoint does not follow the mission waypoint to 2 meters but drops down about half a meter to then slowly ramp up to the waypoint setpoint again. (around t = 3:25 - 3:27)

What process is determining the z-setpoint and how can i make the z-setpoint follow the waypoints as put in via Qgroundcontrol?

Log of the flight above:

Thanks in advance for the help.