I'm fine ditching the switch. You're right that Victron did not call for it. The purpose was simply to be a master battery disconnect, so I could disconnect ALL loads (not just the inverter) on the battery when the trailer is not in use. But I may have to live without the switch, and manually unhook the battery instead when the trailer is not in use.
It would still be good to know what is happening though. I doubt the issue is the switch itself, as it seems to be functioning normally with only the inverter connected through it. My best guesses right now are either:
a) Some sort of feature on the inverter, but I'm still not sure how the inverter could possibly be dropping the battery terminal voltage to zero
B) Some sort of feature on the Battle Born batteries. They have a built-in battery management system, so maybe the batteries are shutting themselves off for some reason when the switch turns on.
I have the workaround for now (only hooking one component through the switch), so I'll proceed with the installation while I'm still figuring out what was going wrong.
