After disappointing experiences with 2 previous 20S Dual sets, I upgraded ad installed my new set (S/N 1408xxx). Immediately a perfect indoor FM stereo reception! But riding experience is quite different!  My S20 is connected to my Garmin Zumo 590 (also latest software) through 'gps-pairing'; no other devices connected to my 20S yet. Riding in an urban area with quite a severe speed limit enforcement I have my Zumo warning me every time I exceed the speed limit. It takes the 20S a number of seconds to recuperate from those single beep warnings and surprises me by jumping to a next stored FM frequency after each warning. I haven't been following a gps guided route yet, but I'm afraid that every gps instruction will lead to a FM frequency shift. What is wrong here? Any suggestions?