Intermittent wipers issue with rain sensor

[Kemper-van]

All,
I have a weird behaviour of my windscreen wipers when using the rain sensor.
During heavy rain with the wipers stalk on the sensor position, occasionally the wipers stop in the middle of the screen with an error message on the MFD display. Switching to manual wipers (ie selecting interval, normal speed, or fast), there is no problem.
But having wipers stop in the middle of heavy rain is a bit scary.

After switching the car off and on, the issue disappears and auto-wipers work again until the next malfunctioning.
Last time, an additional message was displayed saying the traffic sign recognition was temporarily unavailable.

Question: anyone had this issue before?
Could this be a defective sensor on the windscreen?

(note: when the van was at the dealership last time, I asked them to check for errors and they reported the could not find any issues with the auto wipers...)
Will add this on the list again for the next service, but would be good to have some prior insights if anyone experienced the same.

thanks in advance!