ERR_EMPTY_RESPONSE when posting comments

Hi,

My site was working well on my own server, but now in the client’s one, post comments are going to a wp-comments-post.php page and showing a ERR_EMPTY_RESPONSE error.

I tried deactivating all plugins, changing theme, changing the name of the plugins folder, playing around with comments settings… But I am afraid the problem is somewhere deeper. Maybe on the hosting setup (I have contacted them, but have not heard from them yet).

Here’s the problematic site: https://ateneu.elteu.cat/participa/

Any clues?

Thanks