trigger impacting insertion of records

Hi,

I have simple table having structure like given below:

\d bp_ach_trans
                                          Table "bonzipay.bp_ach_trans"
       Column       |          Type          |
    Modifiers
--------------------+------------------------+-------------------------------------------------------------------
bptransid          | integer                | not null default
nextval('bp_ach_trans_bptransid_seq1'::regclass)

filename           | character varying(50)  |
 payment_status     | character varying(30)  |
 settledate         | character varying(15)  |
 payment_pastransid | bigint                 |
 tname              | character varying(250) |
 code               | character varying(5)   |
 error_txt          | character varying(200) |
 routingnumber      | character varying(15)  |
 tracenumber        | character varying(10)  |
 accountnumber      | character varying(15)  |
 bankaccountnumber  | character varying(17)  |
 type               | character varying(1)   |
 amount             | numeric                |
 site               | character varying(30)  |
 accountype         | character varying(2)   |
 tranid             | character varying(15)  |

Triggers:
    ins_ussf_rec AFTER INSERT ON bp_ach_trans FOR EACH ROW EXECUTE
PROCEDURE ussf_accountnumber_update()



the function definition is like below:

CREATE OR REPLACE FUNCTION bonzipay.ussf_accountnumber_update()
 RETURNS trigger
 LANGUAGE plpgsql
AS $function$ BEGIN update bonzipay.bp_ach_trans set
accountnumber=replace(accountnumber,'_',' ') where
left(accountnumber,3) = 'US_'; RETURN NEW; END; $function$


my query is:

when I am inserting around 1000 records in the table having
accountnumber not having value 'US_', I am getting only 300 records
insertion. remaining around 700 values are not getting inserted.

why this strange behavior is happening, as I am not inserting any
record having value 'US_' even after that all records are not
inserting.

Any suggestions are welcome.



Regards,
Atul