Why cant I delete a network object

You will need to remove the object using Network Atlas, Deleted maps, nodes, interfaces, applications and the like remain assigned on the map to the ghosted object you are seeing on your map. In Network Atlas open the map that you want to edit, On the left click the + sign to display all the Map Objects, Select the Unknown Object, select properties from the menu, Delete the association to the deleted map or reassign a different map.

OK thanks for the reply jmodjeski, unfortunately the properties option is grayed out.

This is the view from the browser:

And this is the view from the server:

They don't appear on the map.

above I noticed you have the map highlighted, click on the one of the undefined objects on the left to highlight it, then properties above should be available,

No unfortunately that is the issue:

On the map click on each link on your map, right click to edit properties, I suspect the one of the links is associated to a deleted interface.