Thank you for using GDMS platform! We noticed a similar issue as you reported: the current synchronization method between UCM and GDMS is UCM sends the IP address to GDMS platform, and in this case, if the user uses domain name or NAT in the UCM, it may block the user to sync the UCM to GDMS platform. We have a solution for this issue in UCM device side, which is users can configure UCM server address to IP or domain name to sync the UCM with GDMS platform.
In your case, this is a known issue that when the user modify the UCM IP address, there will be an extra UCM server for GDMS platform. We will improve this issue in GDMS platform: when users modify IP address for the existing UCM in GDMS platform, there will not be an extra UCM server in GDMS platform. You can see the upgrade in GDMS future release.
Thanks for your testing and suggestion!