Just my 0.2 cents from afar. Based on your findings insofar as the charge line (I presume OEM?) from the alternator to the 7 pin connector is protected by a 60a fuse, this might suggest that a serviceable 7 pin connector is good for 60a (or slightly more), and it also might suggest that the camper’s batteries were quite heavily discharged (likely near maximum current receptivity)…
Bad connections (which add even more resistance) may have been downstream of the protective fuse, while contributing their fair share of additional resistance, culminating in a ‘Perfect Storm’ making matters worse…
My guess is that both your alternator and charge line were under an fair amount of a load for an extended time…Just Saying
Phil
