Enfold and 403 Forbidden

Hello,
I have a weird problem. I just migrated a website from dev to prod, and on the new server (which I didn’t set up), everything seems to be fine apart from the fact that I cannot save anything that has to do with Enfold : whether it’s a page where the builder is used, a custom where the builder is used, or the theme option page (I have a child theme). That problem did not happen on the old server. Any idea what could be causing this ? Is there some specific server configurations that could cause that to happen ? Otherwise, the builder loads fine, I can see inside the blocks, etc. I just cannot save anything.

Thanks for your help !