It's quite possible the hub assembly and backing plate have been mis-positioned, probably during the initial installation, but it will require a detailed inspection and close measurements to be sure. That's why I'm hoping the installation guide will be helpful for a knowledgeable troubleshooter to verify.
I'm sure you're aware, but be sure the tire is inflated to the proper air pressure based solely on the weight that tire is carrying. A number of weight measurements are required to determine exactly how much weight each tire is supporting. Let me know if you need guidance for weighing your rig.
But after a close inspection and some crucial measurements, a good tech should be able to determine the cause of your uneven tire wear. I don't think the tire itself is the issue unless the inflation is incorrect for the amount of weight i t is carrying . I 'm guessing it's something peculiar to your trailer and that axle. Something in that alignment is just not correct. Of course, I know you're already aware of that! more