Metal Gear Solid: Peace Walker

[Eric of Awesomeville]

Hi, I'm New here. so! After beating peace walker 2 legitimately, I went back after a bit and it was invincible THEN but not before. so i used the "1Hit kill (Mechs)" cheat. Now even after disabling cheats, it continues. the mechs have no health left and die after, of course, one hit. EXCEPT FOR THE FLYING MECHS. they become invincible and are impossible to beat. I have too much progress to lose it all, so if you could help that'd be great.