I had the same problem and was very frustrated until I spoke to Lippert. The system needs VERY GOOD batteries at full charge. Having my unit in storage, picking it up and heading for a destination was not enough to get an adequate charge on two group 24 batteries.
I upgraded to three group 27 batteries and added one 195 solar panel. Problem solved. I have not had low voltage problems in three years now.
On another note, my battery storage is very tight, making it hard to check water levels. I am looking into a water maintenance system. system