I know that the spline was mentioned not being glued properly. Sure, this could happen but apparently you haven't had an axle replaced, so I'd say that's not the issue here. When I replaced my swaybar with the IPD one, it was no time that my car developed clicking sounds. It was hard to tell where it was coming from. My mechanic told me that everything was tight including the end-links, but that was not the case. With them torqued, it is hard to tell the higher end of them was note exactly right. I replaced them with IPD's heavy duty end-links (you'll have to call and ask for them and they're only a couple more bucks than the regular ones) and suddenly all my front end woes were gone. Get your mechanic to take the end-links loose and see if they have any play in them with the torque pressure off.
--
1998 S70 T5 Emarald Green Metallic, 2004 V70 2.5T Ruby Red, Previous Owner of Black '94 850 Turbo Wagon