Looks like you may have found your issue, but I thought I'd share an issue I had. I'm using Blaine's Johnny Joint washers, and my lower brackets were deformed just enough that the JJ was actually clamped between the JJ washers, but the washers weren't clamping the control arm brackets tight, so the JJ washers were actually sliding back and forth in the bracket slightly, mostly when applying the brakes in reverse, but it started doing it when driving through pot holes and such. Took me a while to find out what was going on. The fix was to weld the JJ washers to the control arm bracket. Just thought I'd throw this out there in case you might have the same thing going on.