Ok so let's delve into why you're more likely having issues with Whiteline, because I had the same issue happen, got a warranty claim, and realized that they've addressed some of these issues. The main issue exists with aftermarket sway bars having too large of screw holes; it's kind of silly and seems bizarre that they would need to go over M10 because that's not really needed if the hardware is 12.9 Grade alloy. I also believe that's an upgrade in general over the factory spec screw diameter (M8).
So, the first versions of Whiteline's end-links had Nyloc lock-nuts. Those are wrong first and foremost. They have since switched to Class 10, distorted thread (squeezed style thread in specific) flanged lock-nuts.
I had issues with the Nyloc nuts backing off quite frequently, because they were the wrong hardware, even when properly torqued. This backing-off allowed the sway bar's larger 1/2" hole to eat away at my threads. So I was able to start a valid warranty claim.
I had also previously installed some proper lock-nut samples we had received at work, and had good results with those, torqued properly (OEM spec + a few lb-ft) of course. They do not make noise or seem to loosen after this, so always make sure you're being methodical with this type of stuff.
I'm also going to add an insert (bushing) into my swap bar when I install the replacement end-links to eliminate the immense slop and ensure this doesn't happen again.
With the squeezed type of lock-nut it's important to use a thread torquing lubricant as well if your ball joints or hardware are black-oxide coated (Whiteline) as we've had some issues with incompatibility between zinc-plated nuts and black oxide screws with thread galling (there's more at hand there as well, not worth going deep here).
In my opinion, the Whiteline end-links are the best options for a daily driven car, since their recent hardware update. The tighter tolerance spherical rod-ends or bearings on Nuespeed or 034 Motorsport products require constant greasing and cleaning for longevity, and dealing with greasing an aftermarket sway bar is annoying enough, now talk about more time. Additionally, there does not exist a proper protection component for rod-ends that is practical to install and service, and that lasts more importantly.
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