Could be a couple of things causing that rear defrost. Try going into the climate screen, press SETTINGS, and choose MANUAL as the CLIMATE TYPE. Somehow, you must have set it for Single Zone Auto. Try that and let me know. Also I found this fix on another forum: "I had to flash it with the "Synch with audio buttons" steering wheel option (even though mine is the base model with none of those) in order for the buttons on the button bar to work. This is a workaround, I was sure to deselect the Synch and Audio steering wheel options as I proceeded to flash the module." Hopefully that helps.