Yes if this duplicate extension appears on any of the phones that the RmCm application user is controlling.
You said the JTAPI application user. Typically this is wrong and is the account used for the CCX CTI Ports and Route Points. Agent phones are associated to a second application user, typically containing the letters "rmcm".
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.