Hello @Professor_25,
Sorry to hear about this experience. Are you facing this problem with only a particular file? Is this file located on a network/removable media? If yes, kindly try moving the files to your computer's internal hard drive and check if it helps.
Also, try granting Full Disk Access to Illustrator by following the steps shared in this article and share your observations:
https://support.avast.com/en-in/article/allow-mac-full-disk-access/.
Looking forward to your response.
Thanks,
Anubhav