Solar battery hiccup

[Plogowoman]

Hello. We own a 2021 Roadtrek that we just love but it has one problem we can’t figure out - The battery level can be at 100% and you run the A/C and microwave or the coffee maker and microwave or any two things at once and it blips to 0% and you have to listen to constant beeping for a couple of hours IF you are in a sunny spot.
Just completed a pricey conversion to BUSS bar system and added another battery for a total of 6 and same thing happens.
Any ideas?
Thank you.