For what it's worth the image restrictions on this forum are also so tiny one cannot simply take a screenshot or record a video to upload the problem. So I've duplicated the settings from the tutorial and set the frequency to (10/3 - 3.33) for the wind modifier and replicated the object settings. The result is still a 'jump' in animation at the 90F mark when it cycles back
Side note: In the tutorial the instructor sets the frequency to 10 creating a perfect loop; it does not do this for me either. When I set the frequency to 10 I still get the animation skip/jump/tear (whatever you care to call it). I'm not sure if that'll help diagnose, but my frame rate is at 30fps, so in theory it should be looping