I had something similar when I had the stock antenna. Turned out it had an internal break near the base. Someone probably pulled on it to aggressively and you could see when you bend it the base bent like it was separated inside. I went with an aftermarket short antenna and the reception is...
A few times I made the mistake buying those. Each time they are in the trash inside of 60 days. For most of my vehicles it is Bosch Icon's or bust. But with my Bronco I will stick with OEM. After 1 year of ownership they are still perfect. Zero streaks or chatter.
Yes, pretty sure all require that. I don't see the need to keep them though. I also have the plastic lower shroud and I cut a 1" slot across the top to open up the access for air to flow over the IC.