It's like this ~ sometimes change is effectuated by putting in a new part ~ like a new carburetor in your '57 Chevy. Sometimes you get a Corvette off the same line.
See the difference?
that is your error. Every change in DNA is evolutionary in nature. The question is whether what the change means is significant, and whether the resulting organism is more or less fit to survive in the current environment. Some mutations are insignificant. Some are devastating.