Been meaning to post an update for a while now, ooops. We spent a weekend at the trailer in February, and I am pretty sure the inverter gave up halfway through. Luckily the batteries were fully charged or it would have been a very cold weekend! After a trip or two back out to take pictures of the inverter we decided to remove it and take it to a dealership. It had very visible signs of overheating. We ordered exactly the same one and installed it a few weeks ago, and everything works fine now
It was a rather expensive and frustrating lesson to always have batteries in!!