Anyone know anything about Stemco Pro-Torq axle nuts?

I've had them on my truck and trailer axles for 4 years. They are one nut with a metal keeper, and so easy to adjust bearing end float without the problems of tightening and adjusting lock nuts.
However, one bearing I've had to adjust twice in a month because it looks like it is grinding into the Pro Torq nut. Have a look at the pic.
The bearing isn't spinning on the axle, but there is a copper colored deposit as you can see, and there is a groove worn in the nut. They are grease bearings. Just wondering if the nut is faulty, maybe not hardened correctly.
Any ideas from anyone that's used these?

 

I just inspected the bearing and yes, there would have been some movement on the axle when it was loose. But I still can't work out why it would have come loose after a relatively short time. The bearing is still a tight fit on the axle so I am reusing it. Rollers are perfect. I only want to to a quick brake job before I go away.
If I adjust to Stemco spec it is still loose. I always tighten to 200 ft lb, then 100 ft lb according to Stemco. But then I tighten until free play just disappears then put the keeper on.
That's the way I always adjusted axles even before these Stemco nuts.

 

That's what it says, but if I do that there is too much free play imo. I like to adjust the nut like I explained above. I always adjust with the wheels on because you can feel the free play more accurately.
I've got one more axle to go, working Sunday worse luck. There was only that one wheel that had too much play. Also I hate grease hubs, too messy lol. All the others on my gear are oil hubs.

 

You can re use the orange keeper, that's the whole point in buying the Stemco nuts. The bearings are quick and easy to adjust. I go on some rough roads and also dirt, so bearings get a hard time. I always make sure I buy US Timken or German SKF, none of this Chinese crap.