Model X Owners. Can someone tell me if their rear window defroster heats up/defrosts all the thew way or only half way. Mine is 2 days old. I notice that it only heats up and shows defrosting capability for the bottom half of the rear window. The top half remains cold and does not defrost. Are the lines at the top for another purpose perhaps antenna/LTE/wifi ? It's easy to test, just turn on the rear and it shoudl start to heat up ...if someone can help me figure it out it would save me a hours of appts at the service center.