can't synchronize video and slides in XOT

Hello,
I'm trying Xerte Online Toolkit on my local ubuntu 14.04 installation.
I need to show a video and display some slides synchronized with the video.
I've created a new "media lesson" and then I've selected the video I want to display in the media panel.
In the second panel, I've inserted a new "Slideshow" panel, and then I've nested three images in it.
Then I've edited the "Synch point" field in each of the images setting the value to 0, 5 and 9 respectively.
When I preview the course, I can see the video in the upper side of the screen waiting to be started and the first slide at the bottom. When I click play on the video, the slide disappears as soon as the video starts, and I can only see the video.
What am I missing?
Below there is a screenshot of the course tree attached.
Thank you.

Hi Alex,

I think this has something to do with the settings. Can you send me a printscreen from the the page where you added your first slide (in your printscreen called immagine 1) and immagine 2?

Bye,
Inge

Hello Inge,
thank you for your reply.
Here are the screenshots attached.
Please let me know if you need anything further.

Hmmm, not sure.
Can you send me an export zip-file so I can upload it in my XOT and see what's wrong?
You can send is to info(ad)12change.eu.

Bye,
Inge