There are a few users who are experiencing changes in their profile. Their profile name has changed from name to name.domain. Don't know whether it's due to a Windows Update, but user's have minimal access to do anything.
It appears these users have been assigned a new SID & no longer loads the old profile.
I found this info from another post, but it's not answering the question why this is happening:
I did some research and found that a key had been improperly mapped: HKLM\SOFTWARE\Microsoft\Wi
ndows NT\Current Version\ProfileList\<SID>\