tuple concurrently updated

My application receives the folllowing error sometimes.

Any idea how to fix ?

Andrus.

7/XX000:Error while executing the query;ERROR: tuple concurrently updated

CONTEXT: SQL statement "DROP TABLE templsabi"PL/pgSQL function "drop_table"
line 2 at execute statement

SELECT drop_table('templsabi');CREATE TABLE templsabi AS
select
toode,
osak as sihtyksus,
partii,
laosumma,

1 as lj, 0 as st, 0 as vm,
0 as kaubasumma,
kogus,
0 as kogpak,
CAST('' AS CHAR(10)) as yksus,
CAST('' AS CHAR(1)) as doktyyp
from HETKESEI
where true
AND osak LIKE 'TARTU%' ESCAPE '!'

AND toode='DIS123103'
;SELECT * FROM templsabi

drop_table is defined as

CREATE OR REPLACE FUNCTION drop_table(TEXT)
RETURNS VOID STRICT LANGUAGE plpgsql AS $$
BEGIN
EXECUTE 'DROP TABLE ' || $1;
EXCEPTION WHEN UNDEFINED_TABLE THEN
RETURN;
END;
$$;