Featured Images Format Problem (Thumbnails)

Hi!

I just launched my website, and the Featured images are not showing properly on the homepage. It’s not the right dimensions; for one article it’s showing the whole image, for the other, just a little part of the image. But in both case, only a little square is supposed to be selected to be shown.

Strange thing is, it was ok in the preview mode.

I tryed to use a Thumbnail Editor, and every thumbnails are ok. I don’t understand. It’s as if suddently, wordpress is not taking the right dimension/thumbnail for the home page.

You can have a look there :
https://www.lesophiste.com

Can someone help me please?