We recommend using the DollyPLUS PRO on perfectly smooth surfaces, so please check the surface quality of the ground for cracks or bumps which may throw it off track.
Also, the DollyPLUS PRO may not stay on the arc if its body is touching the ground, so please check the suspension tension adjustment on the side legs, as seen in section 5 of the DollyPLUS's User Manual below.
Please try adjusting the suspension of the legs to achieve better results.
If you continue to have trouble or questions, please contact our Customer Service team at support@edelkrone.com. We are happy to help!