DHCPv6 - prefix statement removed - renewal continues

[perl-list]

Consider this DHCPv6 network configuration (subnets have been changed to nonsense): 

shared-network SomeNetwork { 
     preferred-lifetime 77760; 
     default-lease-time 86400; 
     subnet6 1234:4321:105:8000::/50 { 
     } 
     subnet6 1234:4321:10b:4000::/50 { 
          prefix-length-mode prefer; 
          pool6 {
               range6 1234:4321:10b:6000::1 1234:4321:10b:7fff:ffff:ffff:ffff:fffe; 
               prefix6 1234:4321:259:: 1234:4321:259:fff0:: /60; 
          } 
     } 
} 

We had previously had pool6{} range6{} and prefix6{} configurations in 1234:4321:105:8000::/50 Somehow these two devices continue to renew their prefix delegation and ip allocation: 
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Jun 29 10:47:28 dhcpserver dhcpd: Reply NA: address 1234:4321:10b:5fff:ffff:ffff:ffff:fffb to client with duid 00:03:00:01:3c:37:86:61:c0:48 iaid = 1 valid for 86400 seconds 
Jun 29 10:47:30 dhcpserver dhcpd: Reply NA: address 1234:4321:10b:5fff:ffff:ffff:ffff:fffb to client with duid 00:03:00:01:3c:37:86:61:c0:48 iaid = 1 valid for 86400 seconds 
Jun 29 10:47:30 dhcpserver dhcpd: Reply PD: address 1234:4321:258:ff20::/60 to client with duid 00:03:00:01:3c:37:86:61:c0:48 iaid = 11 valid for 86400 seconds 
-----
Jun 29 07:15:42 dhcpserver dhcpd: Reply NA: address 1234:4321:10b:5fff:ffff:ffff:ffff:ffb3 to client with duid 00:03:00:01:e8:fc:af:fd:bc:fa iaid = 1 valid for 86400 seconds 
Jun 29 07:15:43 dhcpserver dhcpd: Reply NA: address 1234:4321:10b:5fff:ffff:ffff:ffff:ffb3 to client with duid 00:03:00:01:e8:fc:af:fd:bc:fa iaid = 1 valid for 86400 seconds 
Jun 29 07:15:43 dhcpserver dhcpd: Reply PD: address 1234:4321:258:fcc0::/60 to client with duid 00:03:00:01:e8:fc:af:fd:bc:fa iaid = 11 valid for 86400 seconds 
Jun 29 18:03:43 dhcpserver dhcpd: Reply NA: address 1234:4321:10b:5fff:ffff:ffff:ffff:ffb3 to client with duid 00:03:00:01:e8:fc:af:fd:bc:fa iaid = 1 valid for 86400 seconds 
Jun 29 18:03:45 dhcpserver dhcpd: Reply NA: address 1234:4321:10b:5fff:ffff:ffff:ffff:ffb3 to client with duid 00:03:00:01:e8:fc:af:fd:bc:fa iaid = 1 valid for 86400 seconds 
Jun 29 18:03:45 dhcpserver dhcpd: Reply PD: address 1234:4321:258:fcc0::/60 to client with duid 00:03:00:01:e8:fc:af:fd:bc:fa iaid = 11 valid for 86400 seconds 
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There are no host declarations or anything for these hosts. There were several other hosts in the subnet/prefix who successfully moved to the new subnet/prefix.

Thoughts?