Problem with battery disconnect switch and inverter

[Bobschle]

Had a problem last week with both my inverter and then the battery disconnect switch. It is a brand new Itasca Ellipse. The inverter would not invert when there was no other outside AC source. When I plugged into shore power, The inverter and every appliance running through the inverter would turn off and then on every 60 seconds.

As we were getting ready to leave the campground, I had turned off both battery switches. When I went to turn them back on neither would come on. I was unable to get the engine started. Out of the blue, I reconnected the shore power and the switches worked and I was able to start the engine.

The inverter screen says I have a bad battery at 9.6 volts, yet the battery monitor screen says it is 12.6 volts.

Has anyone had such problems? Any ideas? It could all be associated with a bad set of batteries or some other common element to all these subsystems.

Thanks for any insight

Bob