Timers for questions aren't working correctly on preview--next button not appearing. Ideas?

I'm having participants view several videos as part of my survey, and because some of my earlier participants were skipping them, I have those questions set now so that participants can't advance until they've at least stayed on the screen long enough to view the videos entirely. There were some cases of participants dropping out midway through, particularly in one condition, so I did another preview of that condition, and one of the slides didn't let me advance even after sufficient time had passed. I checked the survey itself, and the number of seconds I plugged into the timer was correct. I'm unsure what to do. Any ideas? (Screenshot of the offending slide's timer attached.)