The OP says that the problem occurs even if the PV wires are disconnected at the shipping container, but not when disconnected at the array.
That implies the wires are somehow involved, but the panels are not.
The OP also says the is no obvious problem with the wires. If the wires have no short to ground, the only thing I can think of is capacitive coupling to earth.
Other interesting points:
- When hooked to shore power the symptoms go away, but that is probably because shore power ties the AC ground to earth Ground.
- The OP reported that when the trailer has a wire from chassis to ground the current on the connection was very low (near zero). (If it is a capacitive coupling between earth and the PV wire, I would expect the current to be low.)
- The OP reported that the voltage between the trailer and earth is AC and there was no DC reading.
I am a visual person so I drew up my understanding of the layout.
View attachment 70079
The only thing that came to mind in looking at the diagram is that there are probably some ground loops....but I don't think that could cause the issue.