Interface Determination Condition does not work

Dear all,

I have one interface in which the Interface Determination I have 2 interface mappings just like the one showed in this link

http://help.sap.com/saphelp_erp2004/helpdata/en/b9/057375d1b3c24f89fccc76aa3f37cf/content.htm

In the payload I have a custom node from extended IDoc which look like this

<ZXXX>

     <FNAME>INT_DETERMINATION</FNAME>

     <FVAL>INT1</FVAL>

</ZXXX>

the custom field with the FNAME INT_DETERMINATION will determine which interface mapping will be generated. In case the value is INT1 interface 1 will be generated, in case the value is INT2 interface 2 will be generated.

So I put 2 conditions at the interface determination, which is quite like the following (for interface 1):

Left Operand                                        Operation               Right Operand              

/IDOCMSG/IDOC/ZXXX/FNAME               =                         INT_DETERMINATION               AND

/IDOCMSG/IDOC/ZXXX/FVAL                   =                        INT1

and the following (for interface 2):

Left Operand                                        Operation               Right Operand              

/IDOCMSG/IDOC/ZXXX/FNAME               =                         INT_DETERMINATION               AND

/IDOCMSG/IDOC/ZXXX/FVAL                   =                        INT2

The problem is that sometimes Interface 2 is created even though  the ZXXX/FVAL value is INT1

Is there anything wrong in the condition? is there any part that I should check?

Any advice will be appreciated

Thank you,