Yesterday I reanalysed all my tracks on an external hard drive and edited some of there tags without any issues yet today when I try to load the hard drive to continue the editing all MIK is doing is crashing even if I only load 10 tracks at a time.
This could be an issue caused by a corrupt database file.
If you are using a Mac, click on your Finder app, then press command shift g to open the "Go to the folder" window. Paste in ~/Library and then look for the Application Support/Mixed In Key folder. Delete all Collection.mikdb files that correlate with your version.
Then, reinstall Mixed In Key and let me know if it solves the issue :)