The contents of the next slide are loading while the current slide is playing. You might want to rethink having videos back to back on every slide. Perhaps you could break them up with some knowledge checks between videos so the learner is answering a question about the previous video while the next is loading. Video is the most bandwidth intense media you can offer. In addition, consider optimizing your video for the bandwidth that is available to the typical viewer. If you videos are HD or higher you might not be providing the best experience for your learners.