Figcaption class changes with image settings

I have a weird problem that I cannot manage to resolve.
I have a Rich Text Area, linked to a CMS.
I insert images in the Rich Text Area, and add captions to them.
If i insert an image on the right or on the left side of a text, all goes well : the caption is well positionned under the image
Capture d'écran 2023-05-25 171041

BUT if I want the image to go FULL WIDTH, the figure caption is too high.

I noticed the margin-top of fig caption is “-20px”. And I think that things have changed, because we can’t style global figcaptions anymore.

So, how can I solve this problem ?