Just copy and paste this command one by on in terminal
apt updateNow restart your computer or logout and login.
apt purge pcmanfm2 pcmanfm2-dbg
apt install pcmanfm
You should remap file manager icon (Launcher) on bottom panel.
Right click on broken icon/ link and go to "Application Launch Bar Settings". Remove older link from left side and add a new one from right side.
I get this tuto from a post in Peppermint OS Forum named "Fixing a crashing file manager".