Expired or crashed browser data and cookies
This error is often caused by expired or cashed browser data and cookies.
The error is often seen for specific user is running Chrome.
Can you please try the following:
(1) Try accessing the site using incognito mode in Chrome.
(2) Use a different browser to verify if the error occurs there as well.
(3) Clear the cache in the user's Chrome browser and retry accesing the page in standard mode.