When I trim audio and video, a section of the cut audio still plays

Using iMovie, I have lined up audio from a mic, and video from an iPhone. But when I trim something out, a small piece of the audio that I've cut, plays still. There is no transition between pieces of audio and video, but it still plays a little but of the cut audio. Despite it not being displayed in the audio waves. So I have to cut a little bit extra off the tail of the audio EVERY TIME I make a trim somewhere. And this is NOT case of not having the most up to date software. (I can't download big sur because it literally does not fit on a macbook of my storage size. And my friend has the most up to date OS, and up to date iMovie, and she's having this problem too.