That's the third time you have said that. Is it doing it yet?
Sorry if I am repeating myself, but I am only doing so to clarify that the battery is not what is concerning me at the moment.
Have you checked the circuit brakers? I had a similar problem not too long ago where while connected to shore, the converter was not charging the batteries and I was getting low readings at the points you just mentioned. I removed all the fuses, cleaned the connections, also at the fuse board, then I replaced the adapter (30amp to 15amp) cause it looked melted on the hot wire. After done all that, I put back all the fuses (including the 30amp fuses), and my batteries charged up back to 12v and the readings were correct again. I don't know if it was the cleaning or the changing of the adapter but it worked. Also I heard on another forum that there is a possibility that the battery isolator switch may be at fault.
Which circuit breakers?
I'm not too concerned about the battery charging, I'm sure that once the main issue is sorted the replacement battery will charge okay.
Which adapter did you replace?
Battery isolator is okay I think. When I have a battery connected the isolator switch just inside entry door does what it should.
There is something else a little odd...
Further diags - I have removed the front of the parallax; the converter is getting 110v, the fuseboard is getting 13.6v from the converter. I removed the positive lead from the fuseboard (that is connected to the battery, allegedly) and whilst the battery has a seperate charger attached , the wire reads 16-ish volts even though the battery that is at the other end reads 9 volts...
I mention this in case it is helpful - I repeat, I'm not too concerned about the battery, the parallax should power the 12v on it's own and that is what I need to fix first