You are not "dense" My Lady!!!! ..... You are at the bottom of the learning curve!!! and accelerating!!!
RVs are complex machines. Sort of like jumping from your Camry (a Piper Cub) to an Airbus 380! One step at a time.
Well anything is possible. Poor, minimal, or lack of care i maintainence is always possible. Could be sloppy work by the techs.... Or more likely the previous owner. DEF will creep through seals and joints anywhere in the system if they are not perfectly clean and tight. A couple drops spilled in the catch groove on the fill port and a week later it looks like frost.
The fill port's cap has an "O" ring seal. It could have been damaged or was missing. New cap should fix that.
But, again.....as Aunte Crow would say: "Cleanliness is next to Godliness!"
So. Use a dedicated plastic funnel. Don't overfill. Mop up any dribs and drabs.
Refill it .... Maybe every 1500 miles...or every 4-6 diesel fillups. Top off when you store it.
