Lots of good suggestions here--a few more ideas:
Lippert adjustment procedure from a 2014 Lippert manual supplied with a Puma trailer is: tighten to 50 ft. lb. (didn’t say spinning, but I would); back off; finger tight; back off until pin or tang aligns. I see that this matches Dexter.
If OP is not using an infrared temperature gun, I suggest a cheap one. Even if inaccurate, you can compare wheels. Would be curious to know the tire temperatures compared to the wheel/hub temperatures. I usually see 10 – 20 degrees warmer on the tire than the hub. Tire temperatures might show a severe alignment problem. Is there any possibility that it is brakes dragging? However, if the wheel turns a whole turn freely, the brakes should be loose enough. Lippert says ½ to 1 turn free. Checking the brake controller (as mentioned) is a good idea.
OP could check angular alignment: move trailer back and forth a half dozen times to take strain from the last turn out of the axles. Drop a plumb line from the front center to mark on the ground. Measure to the front of each lead tire. Should be the same within ¼ inch. Measure center to center on the two axles—should be within ¼ inch.
I’ve had trailers with Alko, Dexter, and Lippert axles. I’m a little under-whelmed by Lippert, but mostly because of weak brakes (and have read of others experiencing weak brakes with Lippert). Never have had bearing problems. Because of weak brakes on the 4400 lb Lippert axles on our Puma 253FBS, I got them switched out to the 5200 lb axles by the factory at a very attractive price. On the last trip last fall, I had one hub heating up. Since I had just adjusted the brakes before the trip, I loosened up the hot wheel—the high temperature mostly went away.
I feel for the OP—lots of stress over this. I would find a truck, spring, and trailer repair place, Dexter if possible. Stay away from the RV stores. This looks like it’s going to need some serious troubleshooting, and maybe just a little professional money spent might solve it. I have a Dexter place in Indy that does this work for less than the RV stores, and they know what they’re doing. If the OP is ready for serious money in replacing axles, I’d go with Dexter first, Alko second.
I’m going to PM the OP with some additional local information.
