If you check the code (https://github.com/hestiacp/hestiacp/blob/main/bin/v-change-sys-hostname), you’ll see that it basicly only replace the system hostname (/etc/hostname). Probaly I would suggest to modify /etc/hosts and /etc/hostname (or use v-change-sys-hostname) - this should be enough for changing the hostname.
Let us know if all worked properly 
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