Joe, we jammed to and from Md at about 75-80 mph with no issues. My trailer was packed so tight we had to sit on it to close it, chairs and full cooler. I saw your trailer and you didn't have half of what we had in your trailer. We do suffer in gas mileage but she pulls sweet.
Thoughts, pull out and check those bearings. Repack them with fresh grease forcing it through the bearing. new seals then reassemble and seat. I seat mine at about 50 ft#, then back off, retighten by hand until it touches and back castle nut off just until you can get the cotter pin in.