Social Share buttons from other plugins randomly work or not on post pages

Hi,

First of all, many thanks for your work 🙂 Really enjoy the Nirvana theme 🙂

I’m facing a strange problem, and I don’t know if it’s linked to the last update, because the website is new and I don’t know if the same problem occur before.

The problem :
I’m using an external plugin to display Social Network Share buttons (Crafty Social Button, and I have also tried Simple Share Buttons Adder), but these buttons appear randomly on some posts and not on others.
I have compared everything between these posts, I see nothing that could explain it.

Is there a known bug about this ?
What can I do to locate the problem ?

I’m using wp-super-cache, but I have cleared and then disabled the plugin to debug the problem.

Just in case, the Social Network Share buttons plugins I have used :
https://wordpress.org/plugins/simple-share-buttons-adder/
https://wordpress.org/plugins/crafty-social-buttons/

Thanks a lot for your help 🙂