I have checked the page on your site from my end with same OS and browser, no problem been found.
We will pay attention to this problem and contact layerslider author, try to find this problems and get a solution.
But now I have an other prob (not related to it, I had it before your update).
On this page http://aston-itclient.bleupetrole.fr/societe/
The arrows of the client module don’t work, they seem to be behind the other blocks and we can’t click on them, but if you refresh the page it works fine.
Can you help me again ?
(I have upgraded your user permissions, sorry I forgot to do it the first time)