I discovered by accident tonight a way to override Siri instructions:-

  1. Press the home button to issue a command
  2. The moment Siri thinks it’s interpreted the instruction, press the Mic button
    (this has to be done *before* Siri acts on the command)
  3. Press the instruction text
  4. You can now edit, change it and hit done when finished
  5. Siri will pick up where she/he left off with the new instruction

I don’t know yet if this helps/affects recognition, just thought I’d let you all know.