Make a backup of your gamelist.xml

If you checked Save old gamelist in the Gamelist Options tab, ARRM will make a backup of your old gamelist, before saving the new one

You can force a backup of all your gamelist.xml by clicking on the Backup gamelists button in the Gamelist Options tab. A folder with the name of each system present will be created in the %appdata%\Nexouille soft\arrm\temp\backup folder which will contain the gamelist.xml backups in the form: gamelist_yyyymmdd-hhmm.xml (example: gamelist_20211119-1955.xml)

You can directly access the backups folder via the View Backup directory button on the Tools tab

Remember to clean up these directories from time to time..