Since a couple of days when i am near an obstacle near the rear of the car, the right front sonar on the screen flash to yellow. It's also super sensitive.

Tghe rear one never flash.

Any idea what might have cause that?

Still doing it. Even If I am near a rear obstacle, only front right yellow sign appears on the screen.

The only time I had weirdness like that with one of my sensor has been when there was ice or something like that on one of them. Does it do it when you are not backing up?

I heard that a recalibration may be required to these sensors. Never needed it. Did you try to disconnect the battery? Not sure if it would do anything but perhaps....?

Well not much ice here. I did tried to disconnect the battery. But i just got a reset from the dealership because of a check engine light.

How can I do a recalibration?

Can’t help you with the recalibration or reset. The dealer did it when I got into an accident. But did you try a good clean with strong detergent? Just grasping at straws here...