BCP Error - Missing Data

After loading the BCP files that are created during the trigger/
reporting events I've noticed that the data in the table is missing
records. I've also noticed that the missing records (records in the
table but not in the BCP out files) seem to occur in contiguous
blocks. Since the complete set of records exists in the table, I
assume this points to an issue in the way the TableUpdate script/
Triggers interact with the system. But i tried to take out the bcp
procedure, do test on trigger, then no data missing, So, I think the
problem is still on bcp part. Could you help me with that?

CREATE TABLE [EventUpdate] (
[id] [int] NOT NULL ,
[eventid] [int] NOT NULL ,
[sequenceid] [int] NOT NULL ,
[UpdatePass] [int] NULL
) ON [PRIMARY]
GO
create trigger trgEventUpdate on EventLog For Insert,Update as
insert into EventUpdate (id,eventid,sequenceid) select ins.id,
ins.eventid,ins.sequenceid from inserted ins



bcp script:

bcp "select a.* from w..eventlog a, w..eventupdate b where
a.eventid=b.eventid and a.sequenceid=b.sequenceid and b.eventid<>-1
and b.sequenceid<>-1 and b.updatepass=1" queryout 30sec-%TFN_NOW%.wrk -
U <userwithaccess-P <password-S doserver -f EventLog.fmt

Thanks in advance for your reply!