Problem happens because sometimes a computer gets a Department entry in Jamf Pro, but the entry is corrupt and Jamf still thinks it has no Department, so Jamf puts it into the "NonStudent - No Dept" smartgroup. You won't see the computer listed in that group, but the policy that runs on members of that group is Faculty Staff Set Department and that policy keeps running on these bugged computers. The policy is also set to cache itself so that it runs even when Jamf is offline, and when the computer first starts up its wifi IS offline (not connected yet), so the cached policy runs.
TO FIX THIS:
- In Jamf Pro, set the computer in questions' Department to None
- Plug the computer in to a wire
- Restart
- Select Department when popup comes up
The computer should now have a non-corrupt Department setting and it should no longer give the popup