If you have been SharePoint Site owner long enough, you would have definitely bumped into task like assigning document permission using SharePoint People Picker.
One of the out of the box SharePoint People Picker features is that it auto caches all previous user entry entered/selected by you.
This cached people picker entity is meant to help you to quickly find the user and assign the permission.
It would introduce invalid entry if there is cease of identity provider (for whatsoever reason that the decision made from the IT management needs us to swing the SharePoint identity provider to other platform).
Things could get messier for those who frequently accessing people picker, to be seeing the old cached user.
Another situation that introduce inconsistency is when there is change of user name/job title etc for which is cached and not reflecting the correct info to the end user.
If you fire up your browser development tool and type in “localStorage” (case sensitive) in the console. You would see the cache key/value for ClientPeoplePickerMRU.
Chrome – Resource tab
So what can we do?
The other possible way is to get them clear the Local Storage from their Browser. I couldn’t find where the IE local storage is. If you know, I will be more than happy if you can tell me.
For IE Users who wish to clear the people picker. Here are the steps you may follow
1. Go to page with people picker
2. F12 Developer Tools
3. Close F12
4. Then refresh the web page to test it.
[Credit goes to Chris for the steps above]