'06' monarch house electronics not working

Just returned home from a short 100 mile RV trip and when I shut the engine down none of the house electronics ie. lights, slides, water pump... would work. When I restarted the engine, they would again operate. They would also work when plugged into shore power. Both the chassis and house batteries are showing ~13vdc with the engine off and no shore connection. The house batteries are 4 Interstate 6vdc deep cycle batteries in the traditional 2s-2p configuration they are 5 years old and have performed flawlessly from day 1. An inspection of the electrolite levels shows all of the cells at 1/4" or greater above the plates. I have a 4 stage converter which is always plugged in when parked. Anyone have any ideas as to what the issue might be?
Thanks
-Rick