Strange DDNS errors

[#1]

We have an Infoblox DHCP failover pair updating MS DNS via Kerberos, we see a lot of messages in the logs like this, does anyone know what it means?...

ddns.c(1871): Invalid lease update. Tried to clear already NULL DDNS control block pointer for lease 10.124.73.69.

[#2]

Here's an example... doesn't seem to causing any impact so guessing they can be ignored...