Your app is probably deployed to more than one target (maybe another cluster or a standalone server). Here's what you can do:
First remove the reference by using "delete-application-ref". Once the reference is removed, then you can do undeploy command.
To find out if there are any references, use the "get * | grep application-ref.<name-of-application>". You'll see a list in dotted-notation. The target is the first value in the dotted-notation.
(e.g. server.application-ref.hello1.* where server is one of the target)
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