Hi Emiel,
Thank you for the details!
There seems to be something wrong with your .htacces mod_rewrite or perlmalink configuration.
When I look at the network tab when loading your site, there are a tons of 301 redirection requests: https://i.imgur.com/VS8L5gC.png
All of them are trying to access the regular ajax handler, but it gets redirected incorrectly to the same URL: https://i.imgur.com/P1TRwha.png
So it ends up in an infinite loop. This only happens when a translation is selected – so my guess is that it’s probably related to a specific cookie or similar.
Make sure the default WordPress ajax url is not added to the translations as it is used across all the website, in your case it’s the https://www.vdvelde.com/wp-admin/admin-ajax.php url. This should always work regardless of the translation and should print 0 to the screen.
