We have 8.5 CUCM so RTMT versions are different but I was sort of thinking along the same lines so I uninstalled both versions and only installed UCCX version and triple checked I was connecting to UCCX.
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.