I finally decided to do something to our loose auto-dimming rearview mirror with HomeLink on Sunday before the weather is getting too cold and the tabs of plastic cover may become less flexible and more fragile. I guess I was lucky none of the tabs been broken after I separated the windshield sensor cover. Again thanks to Kedis82ZE8 otherwise I would need to get the new cover!
The T20 screw holding the heavy mirror was loose. I tightened it up but not too much as I'm fully aware the weak windshield issue on CX-5 and many people had line crack developed from this sensor area due to stress fracture which might be caused by the heavy mirror attached to a small metal plate glued to the windshield, definitely not sensors as these sensors looked pretty light-weighted and attached to larger area of the windshield.
I've seen at least one forum member mentioned having the loose auto-dimming rearview mirror. That's why I went ahead and checked ours for sure ours was loose too. I suspect Mazda is intentionally not putting enough torque on this T20 screw to prevent adding too much uneven force by the screw itself against the metal plate and windshield, hence loose mirror after the delivery. But leaving the mirror loose may also contribute possibility of line crack on windshield as the base of the mirror will keep banging the windshield. To me, the design needs to be improved. At least the metal plate which glued to the windshield where the heavy mirror attached to should be larger and thicker!