Uncontrollable inputs on Melee emulator on pc

I'm using dolphin emulator to play Melee on my pc (windows 10). The ISO works and so do the controller inputs except there is an uncontrollable down and to the left input on the c stick and directional stick that makes the game unplayable. I've tried using a different controller when I unplug the controller or the put the Mayflash adapter on pc mode the bug stops (but then of course I can't play). Please help.