Further testing this and I found that this mostly occurs when increasing collective while decelerating (which you have to do as you get slower to not fall out of the sky) around 140-130 kph. This oscillation then lasts to around 100 kph after which it decreases and ultimately fades away.
Additionally I just found a forum thread on this topic which is marked as solved. The solution is to turn on all of the AP channels however this doesnt affect the problem at all in my testing. I tried to recreate this with roll and pitch autopilots on, then with roll, pitch, and yaw and it happens every time on both configurations. If I disable the pitch autopilot channel however it does stop the oscillations but this isnt a proper solution as you have no pitch autopilot available.