Hello.
I think your problem is your Processing Instructions are getting overwritten. I’m guessing your Send Pipeline is overriding them or not appending them as needed.
Processing Instruction can be set in three ways: inside an Orchestration, inside a map, or inside the pipeline. How they are handled in the Send Pipelines also depends if they exist in the original message.
In my Sharepoint hands on lab, I set them inside the Orchestration but then I use the Pass Through pipeline on the send side.
How are you setting your Processing Instructions? I’m guessing your input message does not have processing instructions?