[CentOS] Bnid Dynamic Update not returnnig latest update

I have a zone that has several hosts update their ip with Dynamic DNS updates.
This morning a client had updated its ip, but bind wasn't returning the new ip
when queried until I restarted the daemon?

Google hasn't yielded anything useful as I am prolly missing the boat with my
search criteria. Anyone got any clues/pointers about this issue?

Thanks,
jlc