[Unassigned Devices]

UPDATE: After running some tests, Bin’s answer helped me out the most!

 

Thanks

[Unassigned Devices]

I will try that, Bin
Thanks for the suggestion!

[Unassigned Devices]

Unchecked Network Polling.
Deleted the devices, and they still re-appeared.

[Unassigned Devices]

Thanks for the response, DonKid

The issue is that the workstations listed in the Unassigned Devices folder have not been in use for a while or have been re-purposed and I cannot uninstall the Network Agent from them. 

[Unassigned Devices]

Using KSC 13.1

When deprovisioning workstations for my company, they are put into the Unassigned Devices folder.
When they are no longer needed, I delete them from there, but they return.

Why is that and how can I delete them permanently? 
I tried right-clicking each individual one and selecting “Remove from Database” but they still return.