According to /etc/mtree/BIND.chroot.dist the permissions of /var/named/etc/named/master inherits an owner:group of root:wheel with the mode 0755. This should either be bind:wheel 0755 or root:bind 0775.
Turning on ixfr-from-differences will cause BIND to try to write a journal file to the master directory, which it will attempt using the user:group of bind:bind. There is no way to force the journal file to any other directory except where the master file resides.
* enable ixfr-from-differences in the options stanza
* update a zone with type master
* issue an 'rndc reload' for the zone
A temporary workaround of moving master files into /var/named/etc/namedb/dynamic is possible, but ignores the conceptual separation of zone types.
Mathieu, can you please take a look?
I'd be a little surprised if this was still an issue. When I submitted the PR (in 2014!) 9.3-RELEASE was the going thing, and BIND was part of the base system. The specific details have certainly changed, as /var/named isn't even listed in the mtree files anymore.