I started hearing my pedal-side chain guard getting rattly so I took it off and re-did the rivets. Now it's sorted.
Of course while doing that I found another issue. My new rear fender was cracked half way through. As it's pre- paint job still, I chose to do some creative custom work with some ally sheet and a rivet gun.
A warning before looking at the pic: some viewers may experience feelings of jealousy at the craftsmanship used.