Last name of contacts already in my database not showing in new contact list

[SIM-Detroit]

Hello.  With existing contacts who are in our database, when we select them and choose the action "Add to list", they seem to migrate to the new list fine, but their lastname is missing.  This only seems to happen with non-new contacts.  Brand new contacts, not already in our database before being added to the first list seem to transfer fine.  Any help would be appreciated. 

[William_A]

Hello @SIM-Detroit ,

I checked your most recent lists, and any contacts that already had last names still have them. Only your most recently added contacts among those lists seem to be missing last names, which is just a matter of uploading them with one to begin with. The last name field wouldn't be getting removed during a list move.