Rain sensor drives you crazy

Hello, since April 2017 we have a new Kangoo Rapid Maxi 110 FAP in the company. So far I am free with the car, only the rain sensor gives time and again reason for criticism. Especially with spray rain the windscreen wiper wipes up to speeds of 60 km/h almost not at all, one drives in blind flight or switches on continuous wiping. At speeds over 90 km/h it works then, but if then only very little rain falls on the disk, does it sometimes constantly wipe?! Switching the sensitivity to the largest drop (symbol on the steering stick lever) also does not succeed. Renault says it is Stamd of the technology, a warranty exchange of the sensor is excluded, because it somehow works! A pure interval operation without a sensor does not work either. Since I have other cars in my fleet and thus good comparisons, I know it is different. I ask for your experiences.