There are a lot more variables...
Is your rig a 50A? Or you are using a 50A to 30A dogbone?
Does it have a transfer switch?
Which breaker is tripping?
How many amps is your converter(charger) draw?
When you say nothing else ON, does this mean the converter is OFF too?
How many batteries do you have?
Does your rig have an Energy Management unit? What items will it shed when connected to less than 50?
Did anyone add a Hot Rod to your water heater? And cheat by plugging it into the same outlet as your fridge?
What is the AC voltage you are connecting to?
Does this happen when connected to other 30A pedestals? or just this one?
I don’t really know anything about your rig...so, I have to aim for general solutions. Dirty contact issues with outlets, plugs, transfer switches, breakers can all cause these problems. The element probably isn’t the issue if it doesn’t cause a failure on 50A.