Have RV Questions? Ask an RV Mechanic Online.
Clean all the battery terminals and leads and replace any that have heavy corrosion between the terminal and the wiring. Have the house batteries load tested (if those aren't the ones you replaced) so you know if they have any issues. Get back to me if you need more later as all follow ups are included in our fee.
Doubtful that the isolator is bad..........
Check the disconnect solenoids and have any batteries you didn't replace load tested. Keep in mind that even new batteries fail at fairly high rates.
Symptoms like you describe point to a battery that has an internal problem. It can work for weeks and then not...........then work again. I replaced one in my wife's car not long ago that did the same thing. Even load testing won't always find that issue.
10-4.........and testing these with a small digital multimeter is helpful here.
Just checking back in to see if you were able to get this resolved or do you still need additional input from me here?