Oracle Text does not return results when String starts with two consecutive vowels

Question

Hi,
I hope someone can shed some light on a strange problem we're facing.
Oracle Database 11g R2 (11.2.0.4) EE 64-bit running on Windows 2008 Server R2.
When I create a context index on a varchar2 column (surname) it works fine when the surname starts with either a consonant or one vowel. But when the surname starts with two vowels it fails to return the record?
Please see worked example below:
create table t1 (surname varchar2(50));
insert into t1 values ('OURS');
insert into t1 values ('JOURS');
insert into t1 values ('ONES');
commit;
-- sync every 10 mins
CREATE INDEX PERSON_SURNAME_IDX ON t1
(SURNAME)
INDEXTYPE IS CTXSYS.CONTEXT
PARAMETERS('MEMORY 50M sync (every "SYSDATE+10/1440")')
NOPARALLEL;
-- no rows
SELECT surname
FROM t1
WHERE CONTAINS(surname, 'OURS') > 0;
-- 1 row
SELECT surname
FROM t1
WHERE CONTAINS(surname, 'JOURS') > 0;
-- 1 row
SELECT surname
FROM t1
WHERE CONTAINS(surname, 'ONES') > 0;
Any help or guidance greatly appreciated.
Thanks,

Answer 1

Wtf?
https://docs.oracle.com/database/121/CCREF/astopsup.htm#i634475
only     then     where
all     do     into     onto     there     whether
almost     does     is     or     therefore     which
also     either     it     our     these     while
although     for     its     ours
select
from v$version
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production    0
PL/SQL Release 12.1.0.2.0 - Production
CORE 12.1.0.2.0 Production
TNS for Linux: Version 12.1.0.2.0 - Production
NLSRTL Version 12.1.0.2.0 - Production
SELECT spw_stoplist, spw_word FROM ctx_stopwords
WHERE spw_stoplist ='DEFAULT_STOPLIST'
order by nlssort(spw_word, 'NLS_SORT=LATIN')
---- snip ----
DEFAULT_STOPLIST    not
DEFAULT_STOPLIST    of
DEFAULT_STOPLIST    on
DEFAULT_STOPLIST    one
DEFAULT_STOPLIST    only
DEFAULT_STOPLIST    or
DEFAULT_STOPLIST    other
DEFAULT_STOPLIST    out
DEFAULT_STOPLIST    over
DEFAULT_STOPLIST    s
---- snip ----