DDNS with /23 network possible with DHCP from a pfSense router?

[matsan]

Running pfSense as a DHCP server in 192.168.216.0/23.
An external bind server is working as DDNS and updates in the forward domain and in 192.168.216.* work when issued from the DHCP server, but 192.168.217.* fails with:

Mar 21 18:53:18 ns named[2759]: client @0x7f87e0066410 192.168.216.4#55214: update '217.168.192.in-addr.arpa/IN' denied

I have setup both 216.168.192.in-addr.arpa and 217.168.192.in-addr.arpa zones on the bind server as separate zones in bind.
I understand that CIDR, reverse lookups and DDNS seems to be hacky at best.
I have tried enabling debug level for the logs in bind and I get very much logged but the failing update is not loggin much.

Any hints greatly appreciated,
/Mattias