MP4 Movies are Playable Twice - Independently of Each Other

MP4 Movies are Openable Twice:

How come when I tap an icon on the Desktop, the movie plays as the icon. And then, when I double click the icon itself, it opens and plays in its own window. As a result, the movie is playing twice: one as an icon and one as its own window. Each can be played or paused on its own.

The interesting thing is that the icon and the window are independent of each other.

So, basically, it is one file being opened twice.

Strange, but so.

This is a home movie -- it is not an iTunes movie.

My MacBook Pro is only where this is occurring; no issues on my other Catalina devices.

Any fix to it?