BUMP for a possible fix.
Just spent the last 2 hours moving seat around. It was definitely coming from the seat base. Lubing everything did not help. The click sounded like it was coming from a stress in the base of the seat. So, I continued up and down with the rear seat base (mine made noise no matter where the seat was relative to front or back on the main rail).
I would hold the seat with different tension moving up and down, with a click about 1 inch from the rear seat base being at the lowest point. As others have said, my click taking off or turning would go away if I moved the base, but would quickly return.
FIX- Well it's either a sticker that I removed, or it is better because I adjusted the two retaining posts
that hold the yellow wiring harness into the bottom of the seat. Both made a clicking sound. I tried to pull the posts out and figured if they broke I would just tape it up or let it float. Couldn't get it out, but moved it enough and when I did boy was it clicking like I'm used to hearing.
If it was the sticker---
The sticker / paper is on the right side, just above the main pillar going left to right (that rotates when you recline or straighten the seat back. I had my seat back off to be able to better see it. After nearly breaking a finger trying to get in there (pliers would be too easy)... I got it off.
Moving seat the noise appears to be gone. If I hold this sticker and brush my finger against the edge, it closely replicates what I heard.
Here's the sticker you are looking for. Good luck! I've been living with this for a long time. Today is a good day.