Inverter Swap 1000 for 2000watts

It's sounding like you've ruled out the RVs wiring as a source of the problem. I'm assuming you had every AC breaker turned on with the freedom bypassed, and when the batt voltage remained at 12.something. That seems to say there's not a 2nd converter, or could you have inadvertently changed the DC wiring setup with the freedom out of the loop? Bench testing the freedom sounds like it's in order. To do it thoroughly you'll need a 12 volt battery on the bench connected with reasonably heavy wires. A clamp meter that reads DC current would make it easier but you can work without it. All you need for an AC load is something like an incandescent bulb, maybe 60 to 100 watts. Even if you didn't need that 2nd freedom, what you're being forced to learn is worth a lot! And when you finally figure it all out, everybody following the thread will have learned things, too.