Is the Index corruped?

[Rabbit]

I write a FOR EACH loop with a BREAK BY option like this :

FOR EACH order-header NO-LOCK,
EACH order-detail WHERE
order-detail.order-no = order-header.order-no NO-LOCK
BREAK BY order-header.order-no :

.
.

I found a very strange case is this query give me 10 records. If I remove the break by option, it gives me 11 records, if I change the break by option to "BREAK BY order-detail.order-no", it give me none! :dead:

Is my database index was corrupted? Somebody help please!!