If I’m understanding the issue that causes the problem correctly, can it be solved simply by letting the battery run down some before it’s time to hitch up and go? The fridge will put some drain on the battery as well on its own, and if it’s unplugged from shore power for, say, and hour or two, before travel…it shouldn’t be getting enough charge from the truck to be fully charged while on the drive? I thought I was understanding that the issue only occurred when the battery became fully charged and would back feed to the truck, but I’ll be the first to admit my battery/electrical knowledge is not my area of expertise. Oddly, the disconnect seemed to work today, but it was only about a 20 minute drive so that could’ve been a fluke.
edit: I also do NOT have solar, so the only charge the battery would get while driving is from the truck.