I don't have this issue on any of my NES systems with the Everdrive. I own both Everdrive N8 NES and Famicom. I use an AV Famicom (with Hi-def NES mod), NES (standard composite), and an AVS.
I have never seen these artifcats on my games, and Metroid and Punch-out! are definitely games I have played on all three systems with both everdrives.