Updater: new version available

Running on NC 9.0.51 on daily channel I updated from 9.050 using the updater app and having tweaked the config as described. Everything went fine.

Now the updater keeps telling me that a new version is available. If I try to run the updater it tells me:
Current version is 9.0.51.
No update available.
Button: Continue updating

Clicking the button does nothing but making another button available:
Button: Go to back to your Nextcloud instance to finish the update

Is that behaviour due to the testing setup (see config / daily) and works as it was to be expected, or is it something that needs attention?

I did some tests as well. I tried daily as well, now it was possible to install the update, but once the update was installed, it said that downgrading is not supported: So they probably have to fix all the version strings: