Hey Emilio,
The issue happens if you open the 3rd tab when the 1st or 2nd tab is open.
This could be a conflict with the latest version of our theme and the native Visual Composer Tab element. Would you mind confirming that by reverting X to the Stable Version available in your Dashboard. The Stable Version download link is located below the Latest Version download button as shown in the following screenshot.
If the issue persists, please confirm if this is a conflict with our theme in general. To do that, switch to the default WordPress theme and deactivate all 3rd party plugins except WPBakery Page Builder.
If this is a conflict with our theme, what we do is post this case in our issue tracker and it will be queued to be investigated by our development team.
Please just note that we do not support WPBakery’s native elements so we can’t guarantee that this will get fixed. With this in mind, I’d recommend that you rebuild your page using our Cornerstone page builder.
Thanks.