Bind9 different answer per ip, possible

To stop bind, the scripts use rndc stop command. Check if you run it by hands if you have the same answer. If it is the case, check netstat -pnlt | grep 953 if bind is waiting for your connections check if your keys in /etc/bind/rndc.key are the same in /etc/bind/named.conf

If you change the keys, you must kill the process as it will not be stopped by rndc, and then restart bind

Of course you need to specify the delegated zone in named.conf, otherwise bind will think it is just a dotted record it should have, since it is authoritative for the pr.example.com zone.

What you want is something like this. In the master named.conf you specify a new zone (and accordingly a new zone in the slaves):

zone "delegated.pr.example.com." { type master; file [db.filename]; };

and the zone file should be:

delegated.pr.example.com. NS nsdelegated.pr.example.com. 
nsdelegated.pr.example.com. IN A 10.11.0.5 ; glue record 

Now the main DNS server and its slaves know about the new zone and things should work.

==== EDIT

Mistake, the SOA record is not in ps.example.com but it is in the zone definition of delegated.pr.example.com. Fixed that.