I became quite concerned as I read your description of the problem. Of course I can't evaluate the cause long distant, but there are certain details that must be considered.
Batteries don't generally explode, so I have to ask what could cause this to happen? The plates could have buckled & shorted, perhaps due to too high load (short circuit). Too high of a charge rate, hydrogen gassing, etc. I would add that an AC voltage applied could cause that result as well.
Since I have just experienced a failure of the Progressive Dynamics 80 amp converter, resulting in a fire under the bed, I urge caution on your part. I'm NOT saying this is what happened or is happening.
If you lost the ground at the campground shore power, even for a short time, it is possible to apply 240 volts to your 120volt rv circuits. This can happen even when plugging in the power cord with the service breaker on. That can apparently damage the converter. In my case, the 12 volts from the battery back-fed thru the burned out convertor diodes, melting the convertor box & burning into my floor more than 1/4 inch. Eventually, the 80 amp circuit breaker in the power compartment tripped.
This all happened with the main dissconnects open, because the converter is always connected to the battery.
As to the converter circuit, one output lead goes thru an 80 amp circuit breaker, to the battery bank (2-12volt batteries connected in parallel. How come only 1 exploded? Maybe it was bad). The other converter lead is ground. I think it might connect to the frame under the floor, though it could run all the way to the front of your unit.
The input is a standard 120volt circuit, protected by a circuit breaker in the panel. You could check for ac being applied to the battery by simply setting your multi-meter to ac scale. If it reads 0 volts when connected to the converter output, or the battery, then all is well.
As helpful as the diagram would be, suffice it that the output is as simple as can be, with the 80amp breaker being the only component between the converter and the batteries.
Had you checked your battery's water levels? Mine have never boiled down, but a near-dry battery could fail a battery in the manner you experienced.
Sorry to go on & on, but yes, I believe you have (or had) a very serious condition. The potential for fire under the bed, or the possibility of hydrogen gas ignition at the battery. But, sadly, I don't have any easy solution.