I have had this issue as well but after checking a few things out I think I figured out what my issue was.

I had one of the bolts back out on the hinge pin brackets and this allowed my lower A-arms to move back and forth ever so slightly. Over time I noticed the rear of the upper A-arm was showing signs of mushrooming at the rear of the arm. I did a couple different things to correct the issue with my Trix.

1) Replaced the stock hinge pins with Mugen MBX5 Prospec hinge pins. These are threaded pins with a nylon lock nut. This allows you to put the desired amount of tension on the hinge pin plates to keep the lower A-arm from flexing.

2) The tie rod is inserted into the upper A-arm and turnbuckle the same distance. This allows you to have more of the rod end in each piece when making your adjustments and in turn not create a weak link on either side of the upper A-arm assembly.

3) I dont run any less than a 2 degree camber on the front end. This is about 1.2-2 threads difference from 0 camber. This also allows more thread contact inside of the turnbuckle and upper A-arm.

4) Make sure when you install your new upper A-arms that you get the tie rod threaded as square as possible on the first try. If you arent square with your tie rod it removes a little more material from the end of the upper A-arm the deeper you thread it in, due to it trying to square itself up.

Hope this helps.