Just one to be sure, this is for discovered hosts, not rebuilding the host, right?
The only issue I am facing now is that once pressing “provision” in the GUI the host to be deployed reboots but it just loads the discovery image again, eg nothing is being deployed.
What’s the content of the GRUB files, are they properly deployed?
I suggest to check Debugging provisioning tutorial, there are some instructions on how to investigate issues with the provisioning