[takinola]

My first thought as well was there could be something emitting an intense signal in the vicinity that is interfering with the connection. However, there does not seem to be anything nearby (like I said, it is on a bridge going over a lake).

[devilbunny]

This isn’t your problem, but I had a 1994 Pontiac Bonneville whose trunk release signal was triggered by some kind of radio signal that was part of a reasonably common system (security? Anyway, this was late 90s). If I parked in certain locations (certain stores) my trunk was guaranteed to open. It was sometimes so bad that I would have to start the car, set the parking brake, shift to neutral (any gear other than park blocked the remote trunk release), close the trunk, and only then get back in, release the parking brake, and drive off. Otherwise I didn’t have enough time to start the car and get in gear before the trunk opened again.

As a practical solution, I used a short bungee cord to keep it from opening far enough to be obvious, and never kept anything of value in the trunk if the car would be unattended.