Right, it sounds more like grey market to me. I can only speak to my experience and they told me I would need to wait until it's "officially available in the United States" before I could get ay warranty service. Yes, if you dropped it on the...
Wow. Until the present admin along with their huge tariff-fiasco, dji was gearing up for shipment of Mavic 4's to the US. I cannot see how you can even begin to think what you are thinking unless of course drugs and brainwashing were involved.
You don't have a theory ... you have guesses that are only supported by the number of other people repeating the same guesses.
It's easy to imagine wild guesses explain an unproven large number of alleged mystery crashes over water when you don't...
Sounds like you're the expert.
Now instead of suggesting things that might cause the issue you are concerned about, get the recorded flight data from some of these mystery crashes over water and find out what actually happened to cause the incidents.
So yeah ... you are just repeating the BS myths that you've heard and thus perpetuating them.
That has nothing to do with your drones-crash-over-water-mystery.
It's about obstacle avoidance might have troubles under certain circumstances.