Graves "yellow flash" bug?

So I was doing a custom game to try out the new Graves. Towards the end of the game there was some sort of yellow flash whenever I auto attacked stuff (champions I think). I also had rapid fire cannon, so not sure if this had anything to do with it. I read one of the discussions over on the pbe boards about someone having a similar issue, except it happened in the jungle

Here is a link to the PBE thread. The issue i have is very similar, except it isn't in the jungle.

http://boards.pbe.leagueoflegends.com/en/c/bugs/TamhK606-rapid-fire-cannon-and-graves-major-bug