Mine wiggles too. When I mentioned replacing that bolt like the service manual says, the dealer mechanics laughed. I put loctite on it though as its an ALOC bolt.
This click is still bothering the heck out of me. Just one click is all I get, almost every time I use the rear brake. Something is shifting.
Next time I have the bike out, I'm going to check that the disc bolts are all tight, but I've never had them off.
Maybe I'll try greasing the bolt body (not the threads), just to give something to fill that gap. Otherwise, I'll let a mechanic look at it!