Hi Gunther,
could you please check if this app is still existing in the mentioned app project in your IEM?
If so, please delete it before trying to push the same app do a different project/catalog.
@pascal The project folder is empty despite of 'authorized apps'... nor can I see any relicts anywhere in the IAM UI which points to the mentioned app registry causing the failure.
That's strange. Could it be you don't have sufficient permissions to view all of the app projects?
Additionally could you check if this app is present in "Submitted Apps" tab in Admin Management UI? If so, you can delete it from there as well.