One Icon Out of Six Not Changing In Dropbox

I have six projects in Dropbox to sync between my iMac & IOS equipment and when I view Dropbox on my iMac although they have all updated OK to Scrivener 3 one of the icons is determined to stay as the Scrivener 2 icon and all the rest have changed.
If I copy and paste that project elsewhere - say on the desktop - the icon is fine and showing as the Scrivener 3 icon.
Why is this be happening and is it important?

It probably has less to do with Dropbox. How icons are applied to items is strictly a function of the Mac, and you will notice any projects you haven’t updated yet might get the new icon as well—they all end in “.scriv”, so to the Mac it’s the same. I’ve noticed that from time to time the icon database gets a little messed up and seems to cache old icons, or sometimes even no icon at all.

Usually running a safe boot (boot once with the Shift key held down, then after logging in, reboot again normally) cycle clears the problem.