This could be a sign that your batteries are being overcharged or in poor condition. Once the batteries reach their full state of charge, and extra power put into them is turned into heat, which can eventually cause gassing and damage the batteries. Older batteries that may have sulfanated to some degree also have higher internal resistance, which can cause them to get warm under high load or during higher current charging.
I would check that your charging systems are putting out the right voltage, and if so then test your batteries - chances are they need ti be replaced. Either way, it is safe to use the camper, but I would not leave it plugged into shore power for long periods.
