The 4#3 had been flying funny for some time with sudden quick left turns and today I couldn't turn right anymore so I decided to replace the tail motor. The replacement was quite easy. Just take the old motor out and insert the new motor. Then some soldering is needed. Once more the little bird flies much better
I also decided to re-arrange the antenna. Now it is placed below the canopy instead of on the right side of the canopy. Hopefully this makes the bird a bit more aerodynamic.