One detail that ruins everything!

This trailer would be perfect but .....
The piece that attaches to the axis of the bicycle wheel has a towing rod in the axis of travel, relative to the longitudinal bicycle. The junction piece to the end of the drawbar which comes to be put on and snap over the previous forms an angle of approximately 30 ° relative to the axis of the bicycle. In between, a large coil spring that works constantly in flexion of about 30 ° when the bike right ahead. Very bad: when you want to turn left, everything goes well for the spring expands (the two pieces are aligned more or less). When you want to turn right, the spring is twisted an even greater angle: something between 30 and 60 ° depending on the angle of the turn. Too much for the poor spring, coming extreme torsion, done ripping the trailer. I fear also that all this does not live very old!
It would have been easy to make a bike next junction piece with a welded rod 30 ° axis of the bike so that it works in the axis of the shaft.
Too bad.