Hopefully I can clarify.
The shoreline is like an extension cord that connects the truck to the building power. We plug it in when we're at station, we turn the truck off and plug in the shoreline. That is supposed to keep the outlets in the back of the truck usable, hence keeping equipment charged.
Truck A) the truck that charges half the time, what I mean by that is, we can plug it in on Monday night and it will charge overnight but plug it in Tuesday night and it won't charge. This could be as simple as user error, not making sure the shoreline was fully plugged in.
Truck B) the truck that has the wires disconnected from the inverter. So it doesn't matter if it's plugged in or not it won't charge.
But both charge when the trucks are running.
I will get pictures when I can, but until then I hope this helps!