You need to check if your WFCO converter/charger is working correctly. I have owned both a 2014 Vegas and 2016 Axis and neither converter/charger worked as it should. After the batteries are fully charged, the converter/charger should go into “maintenance” mode where it drops from 13.5 to 13.1v. If that does not happen and the batteries continue to be charged at 13.5v, that can boil over the batteries, vaporize the electrolyte and eventually kill the batteries. I purchased and installed a Progressive Dynamics PD4655 converter/charger which works like it should. The WFCOs are pretty much junk. However, it is possible that yours works as it should. From your problem, I doubt it.
The converter/charger should also start out at 14.1v if your batteries are below 50% charge in “boost mode”. Neither of my WFCO chargers did that either which meant it took much longer to charge a deeply discharged battery.
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