[Blackdog_kt]

C is the default key command for changing between positions, you say N is also your change position command.

N being next to the M key, if your settings are correct i would suspect some kind of keyboard mix-up at the hardware level. I would try testing it with a different keyboard, or temporarily assigning different keys to it and see if it persists.

Easiest way to test it: repeatedly press your M key or hold it down for varying lengths of time in a text editor. If N characters also come up on the screen instead of just M characters, there's probably some kind of circuit error on the keyboard, or simply some accumulated dust underneath that's pushing on neighboring keys.