Chinook RV

Just purchased a 2004 Premier 2100
While getting to know the unit I have run into some 12 volt issues
I think the Sure Power 135001 has an issue

The coach is in very good condition looks to be Factory from every thing I can see
Low mileage, very well taken care of.....

So rocker switch panel above driver seat Has
Coach Batteries
Generator Start
Boost start

First I need to say I had the 2 coach batteries Load tested and they are good and charged
All connections are clean and tight

If I plug in the coach to Shore Power, I get an alarm to turn on Coach batteries.....Correct and works
If I then unplug Shore power I loose 12 Volts...Issue
If I start the front engine I get 12 Volts.....Correct and works

When I try to start the Generator it just clicks like low Voltage
If I hold the Boost start the Generator starts properly...but when I release the Boost all 12 volts gone
I understand the Onan 4K needs 12 Volts to the unit for it to run

I think the LVD is dropping the 12 volts and is Faulty
Does this sound likely.....
Is there a newer unit that I can replace the Sure Power with
I would like to keep the original design in place but with newer technology

Thanks for any help