Experiment ends due to 'irregularities'

[mbreen]

I am currently running a long (45-60 min) study with kids ages 6-10. Eight have taken it, but 3 show up as 'Abandoned.' One of the 'abandoned' participants emailed me to say that the experiment ended due to the 'detection of irregularities.' This also happened when we were testing the experiment, and I had assumed it was due to the experiment timing out, and so I increased the allowable duration to 120 minutes. But the participant who emailed me was only 45 minutes in when the experiment abruptly ended.
What causes this early termination? Is there anything I can change in the code to keep this from happening?
Thank you!