Thank-you all for your suggestions. I'll check the emergency break pin, polarity at the battery and trace back the 12v wire looking for either a disconnect switch and or a draw (sounds like pulling all of the 12v fuses, checking for a draw and then adding one by one may be the quickest route) when I get home tonight.
If you all don't mind I'll post a picture of the back of the distribution panel tonight. Everything looks untampered from the factory but I recall seeing something that didn't make sense in regards to the main feed coming into the panel and it's relation to the bus bar.
Originally I suspected the adapter as well (and it may still be an issue) but I'm having the same results when I plug the shore line into a dedicated 30 amp RV outlet (which was installed and tested last night). Either way while I don't plan on using the adapter often I do plan on borrowing one from a friend to test as soon as I can.
It appears to be a propane water heater which visually looks to be in good shape. I'll take another look tonight though as I haven't done anything with the plumbing yet (unit is dry for now).
Again thank-you all