X2 on the warranty route.
Most good quality companies will honor their warranties.
Sounds like a BMS failure and generally when they fail, getting them to reconnect is a futile attempt at best.
In the future, you will need to do more than removing the fuse for the LP detector, it isn't the only thing that draws power when things are turned off..
Your RV fridge, 12V radio, furnace and even water heater if DSI all have control boards which are run off of 12V.. Those control boards even when the item is turned off all draw some power.. 12V radio uses 12V to keep your radio stations and memory settings even when powered off.
Add in a battery disconnect switch right at the battery terminal, that will 100% isolate the battery from ever single phantom draw of the RV.