the bushing is a 6 month old moog k3176 with a 7/16 bolt in it. The trackbar is an older jks 0-3.5" adjustable. I've had a hard time with it for some time (the sleeve for the trackbar was smaller than the axle mount hole), and ended up drilling out the stock jks clevite bushing and putting the moog bushing in there.
It's entirely possible that the bushing is shot. I'll get a replacement (they are $10) and give it a try.
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update:
You're entirely right. I went back and looked at the video from my original loose bolt, and you can see the bolt move, whereas with my new problem the bolt is fixed and the bushing seems to compress. Here's my original problem:
video link: Http://youtu.be/bsjx7kikote