error in named.conf

Hi all,

Drawing a blank on this. all clients are statically assigned via DHCP, all have a PiHole as primary DNS, and their default gateway as the secondary. UTM forwards to google DNS. PiHole sends all reverse lookups for non-routable addresses to UTM, and also its regular lookups. Whilst trying to configure 6to4, it became apparent that named.conf is broken (logs suggest it first broke on 13th Feb). Here's the offending section:

zone "16.172..in.addr.arpa" IN {
                type forward;
                forward only;
                forwarders {
                        192.168.0.100;
                };
};

This is the log file content at that time:

2021:02:13-20:01:04 home named[4688]: received SIGHUP signal to reload zones
2021:02:13-20:01:04 home named[4688]: loading configuration from '//etc/named.conf'
2021:02:13-20:01:04 home named[4688]: //etc/named.conf:126: zone '16.172..in.addr.arpa': is not a valid name
2021:02:13-20:01:04 home named[4688]: reloading configuration failed: failure
2021:02:13-20:01:06 home named[4688]: resolver priming query complete
2021:02:13-20:01:11 home named[4688]: resolver priming query complete
2021:02:13-20:01:23 home named[4688]: resolver priming query complete
2021:02:13-20:01:43 home named[4688]: resolver priming query complete
2021:02:13-20:01:44 home/home named: Last message 'resolver priming que' repeated 1 times, suppressed by syslog-ng on 

it only occurs once on that date. it only became a 'hard' problem today when UTM restarted named whilst I was looking at making 6to4 work. 

the issue is the .. in the zone name - my question is how do I fix it and make it stay fixed? I have a single /24 network in 172.16, as well as the ones created by wireless protection. the one network I created was 172.16.100.0/24, and there about 10 static hosts inside that network.

I have edited the file to remove the superfluous period, saved it, after which named did start, but presumably when middleware restarts it will recreate it from the database and it will break again.

Hope you can help.

Thanks

DM