Multiple back-to-back partial responses from the same person

Hi everyone,
I've experienced this strange behavior now on a few of my surveys. I'm running behavioral, cognitive psychology experiments so ideally I'd like a given participant to only respond once. I do have "Prevent Ballot Box Stuffing" checked in Survey Options. However, I sometimes get multiple partial responses which are obviously from the same person. This has happened a number of times now, so it's not just one participant's weird internet glitch. It's always the same pattern: there's a partial response from X-Y o'clock. Then there's another partial response from Y-Z o'clock (meaning, the 2nd response starts the same minute that the 1st response was last recorded). The 2nd response is only partial as well. Then there's a 3rd response from Z-A o'clock (starting the same minute that the 2nd response was last recorded). They come in groups of 3-5 responses like this; sometimes the final one is completed, sometimes not. I can't figure out what's going on; why would a subject do part of the survey, exit, start from the beginning, do part of the survey, exit, start from the beginning again, etc?
Has anyone else seen this or have any ideas as to what's going on? Is there some explanation within Qualtrics? Is it really possible that multiple subjects decide to exit mid-survey and immediately start again from the beginning, multiple times?
I'm attaching a picture of an example (with the actual IP addresses blocked).