iPXE does not autoselect PXE boot image(s) set on the NBS General Settings page for 'unknown, predefined or managed' systems.
There is no error message. iPXE will simply select 'next device'.
There is code logic that needs to change to incorporate values in a configuration file along with values returned from the database.
DS 8.1 RU7 and DS 8.5
Development is investigating the issue.
PointFix is available for 8.1 RU7 and for 8.5
Final fix will be added into 8.5 RU1