Hi,

I am assuming that the list you are copying to is in another site collection am I right?

If I am right the reason that the name changes (not random by the way) is because of the User Information List for the site collections.

When an item is copied with a person column in SharePoint, the user name is not referenced.  Their user number as listed in the hidden User Information list is referenced.  So if the user is user number 10 on one site collection but is 15 on the other site collection, the user that is User 10 on the destination site collection will be displayed.

Resolution.

Unless you sync the two User Information Lists between the two site collections which I have never heard any one do before (and would be an ongoing process) the only resolution is to use an update item action after you have done the copy to update the persons column with the correct user name.