Did your batteries test good? mine are still coming in at 13.6 when tested.
13.6V means your charger is in float mode and doesn't mean the batteries are any good. A fully charged battery at rest will be 12.7V. Did the auto store do a load test?
Have you load tested the chassis battery as that is another issue. You should be able to park the rig for say a month with no chassis battery issues.
With the charger working again - Chassis battery charge test: Turn on the headlights for 5 minutes to drop the voltage a bit. Plug the rig in and check the chassis battery voltage. Wait a few minutes and if 13.2V+ then it's being charged.