I would still suspect a draw, although it COULD be the battery, just not likely

I'd unhook the battery

The problem is, that modern rigs have SO much "soft" controlled devices, things are not like back "in the day" --you turned something off, it's pretty much off.

It have an alarm? Maybe something is causing "false" activation of the flash warning, something like that

Another approach, let's say you disconnect, and that shows the "right track"

Maybe next, remove a bunch of accessory fuses and see if that eliminates the problem.

Last what kind of "load test" are you referring to? If the "load tester" is handheld, in one hand, then "it ain't" --a load tester that is