scroll bars within articles

Hi there,

I’m running WordPress 4.3.1 with adaptive flat theme, with a few tweaks, nothing extraordinary as I’m far from coding god !

My problem is that scroll bars appear on some page at the right and the bottom of the body. Problem appears on some pages, and not on others.
Here is an example :
with scroll bars
without scroll bars

The issue is even harder to solve that it doesn’t occur everywhere, not on my tablet for example. But on my desktop, on Chrome or Edge, the problem is here, and always on the same pages.
And on the “Bons plans” section articles, all the articles have the problem.

I know there’s a bug on my theme, but where ?
I’d be really happy if you can help me !
Thanks in advance !