I originally had a problem where my SharePoint users display names were set to something like this: i:0#.f|admembershipprovider|swealti.
I used a PowerShell script to fix them and set them back to DisplayName = swealti (for example).
I have been monitoring the status of them every other day using this PowerShell command:
Get-SPUser -Web "https://mysharepointwebsite.com" | format-table -auto
This gives me a nice look at the users and display names. Yesterday I noticed taht one of them somehow got flipped back to i:0#.f|admembershipprovider|swealti. How do I figure out what is causing this?
Update: I know this sounds like a user profile service issue. I need help understanding how this could be though. The user profile service synchronization timer job is set to disabled (and has been since the site went live). It does sound like a user profile service synchronization issue but I don't understand how it could be if the timer job is disabled.