Can't select Agent Policy when trying to add agent

I restored a backup on my test cluster with ELK stack version 7.13.3, then directly upgraded everything to 7.14.1.

Now when looking at fleet, I'm at the stage of adding a fleet server, the second point: Select an Agent policy, the drop-down field is empty.

Above it says I shall use the " Default Fleet Server policy", so I swtiched to the tab "Agent Policies", but only found the "Default config" and "Default Windows agent with metrics" policies.
I went ahead, and created a policy named: "Default Fleet Server policy", but didn't configure anything special.

Then also I had this new policy in the list in the "Agent Policies" TAB. Then I switched back to the "Agents" tab and got an error:

Configuration Error 
Agent Policy 'e6ad0600-1562-11ec-b3ef-4fee36c13301' already exists with name 'Default Fleet Server policy'

I tried both, Firefox and Chrome, but the Agent Policy select dropdown box stays empty.

How can I get rid of the Error, want to delete the Default fleet Server policy I created, but there don't seem to be an easy way in the UI to do so?

Sebastian