I have a form where at least one of the 3 fields (e.g. f1, f2, f3) has to have value. Field f1 is a lookup field. To serve the above condition I have applied a business rule which works fine in normal scenario. But if I enter some incorrect value in F1 (which is lookup value that does not exit) and save form, I get the error. But if I remove that wrong value from F1 and save the form without entering anything in f1, f2 and f3 the business rule does not fire off.
Is this an expected behavior or a bug?