30 Amp fuse blows with shore power

I have a 2010 Jayco 5W. On our trip last month, when I turned the generator off, there was no power. The 30 amp fuse to the batteries (2 of them) had blown. I changed it and didn't think anything of it. I only ran the generator once on that trip.

I brought the 5W home last night and plugged it in to get ready for a weekend trip. After a while I checked and saw the fuse was blown. I changed it again. After a while, checked the wires, noticed they were getting hot and while I watched, the fuse blew again. I checked the converter and have 14 volts to the battery; checked the leads at the battery and have 14 volts. When not on shore power or generator, everything runs fine from the charged batteries.

Any thoughts as to what is wrong?