Parallax effect with Drupal and Bootstrap

Hi,

I followed the tutorial below to create a parallax effect on the home page of my site.

https://www.ostraining.com/blog/drupal/add-parallax-styled-blocks-to-your-drupal-8-theme/

The parallax effect works very well for the anonymous user.

https://i.stack.imgur.com/xzAVC.png

When I log in with a user or administrator, the parallax effect does not work and white space is displayed between the blocks.

I do not understand where the problem comes from. An idea ?

https://i.stack.imgur.com/UccJd.png

You can do a test on my site :

https://www.s1biose.com

The user ID and password is “demo” without the quotation mark.

Drupal version: 


Source: https://www.drupal.org/taxonomy/term/3/feed