traxxion dynamics makes a plastic buffer thing for my bike that keeps it from rubbing. they said the R6 is bad for it. which turns the oil dirty with a lot of metal particles. Omni Fork Spring Buffer Kit
they said it keeps the spring centered and from deflecting to the side. which is what the noise you hear is.
you can take the cap back off and try centering the spring again. I got mine to stop by doing this but I installed new springs and put the buffer kit in and now it never makes the noise after a oil change.