Hi Sherin,
PI is working as per the pipeline steps where in your message spilit/branch happens post Interface determination. In your 2nd case, Field1=100, Field2=89, your first pipeline step which is the receiver determination says the msg shud be sent to rec A and Rec B. However when it comes to Interface determination for A it does not get one as the conditions differ and hence it fails.
However can you please confirm if you have ticked the maintain order at run time check box in the Interface determination. Ideally even this will not help. However can you please try this out and see if the interface works. Believe it shud not, however worth giving a try. Let me know
Regards,
Sriram