use of transform validation of BODS

I ENCOUTERED A technical problem with BODS SAP.

The version is SAP BusinessObjects XI 3.2

Database Oracle 11g

I am using a function that return a output  value from a input value.

Ex:

begin

                if ($ID_TxRbs = 1)

                               Return 0;          

                if ($ID_TxRbs = 2)

                               Return 15;

                if ($ID_TxRbs = 3)

                               Return 30;

                if ($ID_TxRbs = 4)

                               Return 35;

                if ($ID_TxRbs = 5)

                               Return 65;

                if ($ID_TxRbs = 6)

                               Return 100;

                Return 300;                     

End

Than I have a transform Validation that return an error if the value  equal with 300

Sometimes, it occurs that the function did not recognize the input value ( for ex input value = 5, and the function returns default value  300)

And the validation transformation take the line with the value =300 to the Pass way flow  instead of taking it in the fail way flow.

This  error happens randomly. For example, on 5 hundred lines, its occurs on only for two lines.

1. The type of the field is VARCHAR2(1024) . the received number of character is 1 in the field à ( length (TAUXREMBOURSEMENT)=1).

I don’t understand why this error occurs and why the validation transform doesn’t work properly all day.

Can you help me please?

Best regard