If your SharePoint environment is like ours and you wait a while to install hotfixes, Cumulative Updates, and Service Packs.
We recently discovered a problem with the following critical hotfix from Microsoft for SharePoint.
The issue we’ve run into and I believe there have been quite a few others also running into this is that in 2013 sites, when you attempt to Edit a list item that has a Person lookup field populated, upon editing, the field will go blank. If the user doesn’t realize it, they will save the list item and the person field is now blank. Data is lost.
I found the resolution was to Install the September Cumulative Update.
But, if you’re like us, and need more time to test the CU, you can simply install the below hotfix, which specifically addresses the issue.
There is no reboot required for this install and it will fix exactly this issue.
I hope this helps those of you having this issue. If you’re not aware of the problem, check the article, then check your farm.