If it takes 72 muscles to produce human speech, if one of them stops what happens. no sound at all? or a little unstable?

A good way to think of the answer is this:

Have you ever had dental work done that required a local anesthetic ?
Like having a cavity drilled out, and replaced with a filling in your tooth ?

The injection of 'novocaine' or lidocaine made the tooth and the tissues around it
numb for a while.  The shot also may have incapacitated some muscles on one
side of the throat, the face, or the tongue, and until it wore off, you may have
found it uncomfortable trying to talk right, and your speech may have sounded
funny.  That was an example of exactly the situation your question describes.