COBCH0857: System Error failure during ILASM phase

Error 1 COBCH0857 : System error - failure during ILASM

method-id ReturnNBTransDTO private.

       01  oNBTransPolicyRTSKeyDA type NBTransPolicyRTSKeyDA.

procedure division returning oNBTransDTO as type NBTransDTO.

    set oNBTransPolicyRTSKeyDA to self::ReturnNBTransPrimaryKeyDA()

      set oNBTransDTO to oNBTransPolicyRTSKeyDA::GetData()

end method.

 I keep getting this error intermittently when I compile the above code .  When the error does appear it appears in white space prior to the following code.....set oNBTransDTO to oNBTransPolicyRTSKeyDA::GetData()

The project where this code is included has an Interface class and as soon as I exclude the interface from the project and comment out the code that uses this interface the solution compiles successfully.