Sorry to hear about your experience. Would you mind sharing version of OS & Illustrator? Are all these files saved on a network drive? You may also share some sample files with us to check. Please try resetting the preferences of Illustrator once and see if it helps. Please follow this help article to do that.
**Please note that resetting preferences will remove all the custom settings and Illustrator will launch with default settings. You can also take a backup of the folders in case you want to. Location is mentioned in the article.