@nils-sdun, sorry for the inconvenience the replacement RoboVac caused! Please be assured that we always stand behind our products and we are happy to assist you with an exchange if the problem turns out to be with it.
Could you please clean the bumper with a dry cloth for a retry?
Also, kindly advised that the RoboVac detects with infrared ray and very dark-colored objects/ carpets/floors absorb the ray, so the RoboVac will not be able to recognize them. Could you please put the Robovac in a place surrounding by the furniture in the light color for a retry? Meanwhile, there is the gap between the sensors around the bumper, so the Robovac sometimes can’t sense the thin chair leg. Hope you understand, and we will make it better in the future.
If the issue persists, could you please contact us via our "email@example.com" so we can assist you further? We will glad to help you exchange or return it once we confirmed your order detail and the issue.
We appreciate your time and look forward to hearing from you.