Normally, the feature slider is used to include a large image and create a link. While video may be included, it's not advised for videos that exceed the duration of the transition. What happens in such cases is that the slides transition while the video is playing. You have 2 videos embedded in your slider. Additionally, you've created a feature slider that also is used on other pages. Oddly, the last good transition in your slider is exactly where it begins in transition on the individual pages. http://www.fedesarro...ncia-economica/
Where it seems to break (Slide 4) is either not complete or is broken itself on its corresponding page http://www.fedesarro...tas-de-opinion/
(note... no image there).
I'm not sure how you did this, however, it appears they're all connected and that it's either the order or the slide http://www.fedesarro...tas-de-opinion/
that's causing the transition problem on the main page. I must point out it seems to break at various places in Firefox. I've had to click a slide navigation at 2, 3. 5 and 6. Something is causing the transition to break.
See one of my sites (I'm an economist) to see how it basically should be running. http://www.epicurusgroup.com.
For the videos, I'd strongly suggest using a specific video gallery plugin which would be more effective OR, capturing an image from the video and using that as a link to the video embedded on a page or post.
As for this problem. Since I don't know how you created that feature in the pages, I don't know how to stop this transition problem. Could you explain a bit further how that was done?