I have a list in which there is a people column. I used to be able to filter the list by empty values in the column, but that has abruptly stopped working. That is, normally, I should be able to click on the column header, select the value "(empty)", and return any items in which no value has been entered.
I've created new lists on the same site and been able to filter normally. I've also saved the list as a template, recreated it, and been able to filter normally. Additionally, my database team has not been able to find anything wrong.
Does anyone have any ideas as to what could be the cause, or (better) fix?