Machines in discovery have hostname of "fdi"

we recently upgraded our discovery image from version 3.1.1 to 3.4.4. Since this machines’ hostnames are set to “fdi” instead of their mac address.
We set the discoverd>Hostname facts setting to discovery_bootif fact

Expected outcome:
machines’ hostnames are their mac address

Foreman and Proxy versions:

Foreman and Proxy plugin versions:
discovery-plugin 8.0.1