I was performing some testing of integration with NiFi Registry. I started with an insecure registry running on http://localhost:18080
I created a simple dataflow, called 'Inner Flow'. I then versioned it. Afterwards I put its parent Process Group ('Outer Flow') under Version Control.
Everything worked as expected. I then wanted to verify that things still worked when secured. I secured my registry, changing the URL to https://localhost:18443
Unfortunately, this resulted in no longer being able to check out the flow 'Outer Flow'. It failed because when the flow was created, it stored the coordinates of 'Inner Flow' as http://localhost:18080/.... but now it can no longer find any Registry Client that can handle http://localhost:18080/... since the client has now been reconfigured to use the HTTPS based URL.