Thanks for reporting this issue, Illustrator team really appreciate this.
Unfortunately we are unable to reproduce this issue in house, Kindly help Illustrator Team to nail this issue down further:
Kindly provide the exact preferences you are using and the data from below mentioned location .
Mac:- /Users//Library/Preferences/Adobe Illustrator 2X Settings
Win:-C:\Users\\AppData\Roaming\Adobe\Adobe Illustrator 2X Settings
Share the above information with us at ShareWithAI@adobe.com in a Zip file. Please mention the title of this issue as the subject of the mail.
Thanks and Regards
An error occurred while saving the commentMonica commented
It's July 2020 and every time I open Illustrator 2020 it welcomes me and loses all my preferences. It's really annoying so I will just continue to use 2019.
Felt validated searching Google and finding this thread with so many people experiencing the same thing (since 2018 no less)