Shock tower damage - how did this happen?

I noticed the left front shock on my drives was sloppy up at the top where it's mounted. So I took it off and the holes in the mounting bracket are wallowed out like somebody counterbored them. The shock actually did that to it. The one on the other side was not sloppy but just to have a look see I took it off and it was starting to wallow out the same way. The brackets on the top at the back axle are not like this. This is an AG380 suspension. I have no unusual wear on my tires. The only thing I can figure is maybe it was because I re-used the original self locking nuts and bolts when I put shocks on it several years ago? I dunno??? Weird.

 

Now that you mention that it was a booger to get off there with a half inch impact and none of the others were like that. I didn't look too close at the threads I bet they are messed up. Seems like I used a 3/4 impact years ago and tightened them up really good. But I guess maybe not.

 

Yeah sitting in the driveway like that for weeks on end is actually harder on equipment than driving it don't you know?.?

 

These are aluminum and I'm wondering if the new ones are too.