Hi Amie! I previewed your study and took the liberty to add submission_point back to most trial templates. I did observe what you described - so counting Mississippi is pretty darn accurate! 
Then I realized, if a trial is the last trial of a block, then FF *always* submits response data to the server to "save the progress". Could this explain why the second or third instance always seems to take a bit longer (depending on your procedure configuration), because they happen to be at the block boundary?
Is there a way to reconfigure your trial templates and procedure so that a single "trial" (your sequence of screens) is not split up into multiple blocks? The "alternate" pattern is not limited to two trial templates. So maybe you can link everything together?
Then I realized, if a trial is the last trial of a block, then FF *always* submits response data to the server to "save the progress". Could this explain why the second or third instance always seems to take a bit longer (depending on your procedure configuration), because they happen to be at the block boundary?Is there a way to reconfigure your trial templates and procedure so that a single "trial" (your sequence of screens) is not split up into multiple blocks? The "alternate" pattern is not limited to two trial templates. So maybe you can link everything together?