Actually, it's cross polarization that causes blackout (e.g., the first only let's one direction through, the second only lets the other direction through, so together they let nothing through).
My only, not directly helpful, suggestion is to NOT get the Garmin GPS with integrated camera. Every time it briefly loses wireless connection, then comes back on, it switches from GPS to the camera. So annoying that I don't use the camera anymore. And I've got a pretty small trailer, can't imagine it with a longer distance for the signal to travel.
2018 Jayco 195RB
2014 Toyota 4Runner