Inverter

[Big 386]

Hello
I have a 2016 Heritage Glen 386 fbk the unit has a wfco inverter to run the residential fridge. When I picked the unit up the led read out read 12.5 and the green light was on. Now the yellow light is on and the read out is 11.6 with the empty battery icon flashing fridge is still cold however and the panel for the battery reads full this unit has two battery. I have had this to the dealer for this issue dealer stated it was the truck. I don't believe this as I can have the unit plugged in at camp for three days and as soon as I unplug to go home and turn the inverter on it goes back to 11.6 and the yellow light is on as well. Any advice you could give me to go back to the dealer with

[Bama Rambler]

Need to have the batteries load tested.

Were the batteries in the unit when you purchased it?
Is there a date punched on the batteries?
Are the batteries wired parallel?