Before change the Idrive sensor, Try this easy step to clean the sensor first. My X5 E70 2008
Before the push button stops, there were few signs including the screen was blinking and it changes the setting by itself. Anyways, the push button was not working while others (Left / right) was working. So, I decided to take it out and see how it works before I replace it. It was very simple. If it is not working with this cleaning process, I think you have to replace the whole part. it costs about $400 at dealer shop.