Rain Sensor Malfunction

In my 2012 model 5008, the rain sensor is running fast, whether it is raining or not. Service said chronic. The gel needs to change, but the glass will change in the gel, he said. It didn't make any sense to me. I said why should we replace the glass without gel for the gel. The question remained unanswered.

Does anyone have this problem and have a solution?

In some models, they change the gel. I couldn't find anything about 5008. Call the authorized service, I think. Maybe there is no gel in the market.