Expensive fun does not last long

Have the Hexbug seen at a buddy and was totally begeister, shortly after I ordered myself a. Initially this worked beautifully, after a while, however, he was only running in circles. Initially, the radius of the circle was still relatively large, so that did not bother. Over time, this problem has worsened in the Nanobug; mitlerweile is the radius of the circle at approximately 10cm. This is not acceptable for the price in my opinion.