TX-row lock event wait occurrence and empty blocking_session info

Hi,

Please anyone call tell me if this scenario makes sense ?

SELECT
-- Waiting session details
s.inst_id AS waiting_inst,
s.sid AS waiting_sid,
s.serial# AS waiting_serial#,
s.username AS waiting_user,
s.event AS waiting_event,
s.blocking_session, s.seconds_in_wait
FROM
gv$session s
WHERE
s.event = 'enq: TX - row lock contention' ;

WAITING_INST WAITING_SID WAITING_SERIAL# WAITING_US WAITING_EVENT                            BLOCKING_SESSION SECONDS_IN_WAIT
       4          29           38199 SIU        enq: TX - row lock contention                                        7790

       4         515           25176 SIU        enq: TX - row lock contention                                        1621

       4        1031           38884 SIU        enq: TX - row lock contention                                        7790

       4        2016           19537 SIU        enq: TX - row lock contention                                        7790