This problem is resolved in the upcoming UIM 9.0.
The following workaround should fix the problem:
- deactivate the discovery_server
- make a copy of discovery_server.cfg
- remove the following lines from discover_server.cfg.
only_network_interface_config_items = true
included_probes = "probe1, probe2, probe3, etc"
- activate discovery_server
- make the change in the USM and wait for it to be saved
- deactivate the discovery_server, restore the discover_server.cfg backup and activate the discovery_server again