Hi Nawaaz,
Sorry to hear about your experience. Would you mind sharing the version of the OS & Illustrator? Do you see this behavior with a specific file? Are these files saved on a local drive or network? This information would help us assist you accordingly.
Additionally, please try the suggestions given on this community post(https://community.adobe.com/t5/illustrator/resolve-slow-performance-and-unexpected-behaviors-in-illu...) & let us know if they help.
Looking forward to your response.
Regards,
Ashutosh