Hey, I'm currently having the same problem... kind of. We were camping for a few days and towards the end my tanks were full. I hitched up and took it down to the dump station, came back and unhitched. Last camping trip I had a bit of a scare when the trailer rolled about 6" after unhitching so this time I pulled the breakaway just for added insurance. I meant to plug it back in as soon as I finished but had 3 little ones running around and I got distracted and forgot...
Next morning I got up and started up the Honda to assist with readying breakfast. Ran the genny for about an hour and shut it off. I went inside for something and noticed I had no power. Went up to the batteries and saw that my in line 30 amp fuse and holder were completely melted. My buddy who is an electrician took a look and we discovered that when plugged into 120 (the genny or house) that the fuse will get hot and start to melt. He found that when plugged into 120 that the fuse wire attached to the positive terminal draws 38 amps?
I charged the batteries for about 5 hours using the gator clips that came with the genny The two six volt batteries were reading 5.6 volts each which seems pretty good? Regardless the fuse still melts when plugged into 120.
So the trailer is currently at the dealer. The tech strongly believes the batteries are still very low and drawing the extra amperage so he left them on charge all day and all of tonight... I guess we'll see.
On a lighter side... I did spend a number of hours checking out the 2015 Jay Flight 23MBH.
2012 Jayco X19H
2012 Ford F150 Ecoboost w/ max tow, 4 door w/ 6.5 ft box, 3.73 gears.