Manual insert of credentials into radcheck row disappears after five mins ( MySQL )

[Sophie Loewenthal]

Dear everybody,

    I was asked to manaully add a user into our Radius db for some
thrird party monitoring. Sometimes when I insert the row it's there, but
after 5 mins or less the row is removed, as shown below.
Does some Radius process remove rows?


* First attempt *
mysql> INSERT INTO radcheck (id, username, attribute, op, value) VALUES
(DEFAULT,'xmonitor1','User-Password',':=','xxxxxxx');
Query OK, 1 row affected (0.01 sec)
mysql> select * from radcheck where username = 'xmonitor1';
Empty set (0.01 sec)
    (Disappeared immediately!)

* Try again *
mysql> INSERT INTO radcheck (id, username, attribute, op, value) VALUES
(DEFAULT,'xmonitor1','User-Password',':=','xxxxxxx');
Query OK, 1 row affected (0.00 sec)
mysql> select * from radcheck where username = 'xmonitor1';
+-------+-----------+---------------+----+---------+
| id    | username  | attribute     | op | value   |
+-------+-----------+---------------+----+---------+
| 65745 | xmonitor1 | User-Password | := | xxxxxxx |
+-------+-----------+---------------+----+---------+
1 row in set (0.00 sec)
    ( Now it's there)
    ( Let's wait 5 mins and try this query again )
mysql> select * from radcheck where username = 'xmonitor1';
Empty set (0.00 sec)
    ( Opps. now it's gone )
    ( Let's see if some other entry took this id )
mysql> select * from radcheck where id = '65745';
Empty set (0.00 sec)
mysql> select * from radcheck where id = 65745;
Empty set (0.00 sec)
    ( Nope ).


Operating System:
CentOS 6.2

RADIUS Server:
freeradius-mysql-2.1.12-1.el6.x86_64
freeradius-utils-2.1.12-1.el6.x86_64
freeradius-2.1.12-1.el6.x86_64

MYSQL server:
percona-xtrabackup-2.2.9-5067.el6.x86_64
Percona-Server-shared-56-5.6.21-rel69.0.el6.x86_64
Percona-Server-server-56-5.6.21-rel69.0.el6.x86_64
Percona-Server-shared-compat-5.5.30-rel30.2.508.rhel6.x86_64
percona-toolkit-2.2.3-1.noarch
Percona-Server-client-56-5.6.21-rel69.0.el6.x86_64


I'd be very grateful if somebody could let me know how I could diagnose
this, or perhaps tell me the right way to insert a username+password
into Radius.

Kind regards. Sophie