As the other response notes, any kind of flashing screen issues relate to the 10NES lockout chip not communicating properly with the cartridge. Disabling the 1

As the other response notes, any kind of flashing screen issues relate to the 10NES lockout chip not communicating properly with the cartridge. Disabling the 10NES would solve the flashing part, but if you're getting it with a solid color screen instead of the opening second of the game you have a few other pins that aren't connecting well either. The front loader NES has a design flaw that makes the cartridge slot wear out over time and the pins stop making good connections. It wouldn't surprise me to find out that the Game Genie aggravates this flaw because of the way it sits in the slot, but every front-load NES is doomed to eventual failure if it's actually used. Fortunately there are cheap replacements available and it's a pretty trivial job to install them. It's basically just a C-shaped bit of plastic and metal that connects to an edge connector on the NES motherboard and then loops around to face the cartridge slot.