can't update subserver IPv6

When I try to update a sub-servers IPv6 and use the 'already active' option I still get a error and VM will not make the change

Updating IP addresses in virtual server
Adding IPv6 address 2607:f1c0:81a:e000::9 ..
Failed to change IP address : Failed to add IPv6 address : SIOCSIFADDR: File exists

Call Stack Trace

File Line Function
/usr/share/webmin/net/ 320 WebminCore::error
/usr/share/webmin/virtual-server/ 363 net::activate_interface
/usr/share/webmin/virtual-server/ 36 virtual_server::activate_ip6_interface
/usr/share/webmin/virtual-server/save_newip.cgi 306 virtual_server::setup_virt6
(eval 74) 6 (eval)
/usr/share/webmin/ 2386 (eval)
/usr/share/webmin/ 914 miniserv::handle_request



Is this IP already active on your system, and you are just trying to associate it with an existing subserver?