We have frequency problems - of 3 increased to 5 star, after problem-solving!

After we bought last year that Mario car for our great, this year our little boy was my turn and got the Yoshi-car. Drives each alone in his car, it is super- giant fun. So I emphasize all the positive reviews and comments by previous speakers !!! Unfortunately, there are still problems with us, when both cars are driving along / parallel. This is where the remote control of a Yoshi to Mario. That Mario travels when but Yoshi moves the remote control of Mario is off (I hope I can follow?) And Mario travels and Yoshi stops. Despite "the most accurate" to follow the instructions, the frequencies get in the way. Tears stay there is not enough. Now we have turned us on Carrera and wait for what they suggest us. Information will be updated ...

Addendum, 04/19/2015
We have turned to us with our problem to the customer of Carrera and we have to say, good service. After relevant problem analysis two new controllers were sent on goodwill us. We tested with these different scenarios to recreate existing problems before, nothing happened more! Both are now driving flawlessly, no interference of the frequencies more. Carrera (Stadlbauer) has also reported much faster than was expected. In her email stated initially that one should wait with an answer, but already next day was responsive to our problem.
So, everything was great!