Hello Erwin
Unfortunately we have only now discovered your question, please excuse us! If the problem persists, please contact us directly. We can be reached by e-mail at service@irobotics.ch or by phone at +41 62 746 06 74 and would be happy to help you.
Best regards,
Your iRobot Team

A reset can be triggered by pressing and holding the start button. But will that help? Cleaning the sensors for tuck detection might help. Have you already tried a different cloth?