I have a feeling this may be to do with the Querystring constraint in the 'Filled out form' filter. As I have identical smart campaigns (same flow steps) but the only difference is we a particular Querystring instead of "is not empty".
The one thing I still have not seen a screen shot of, which was the first question asked, is what is in the smart list?
I see a choice for Filled out form in the flow step, but if the filter for Filled out form is not in the smart list this will never work. Can you please share a screen shot of the smart list?