Is it possible that eventsbooking got issues with the correct cart / ID settings in checkout if you use SEO urls like:
yourdomain.com/index.php/tickets
that if you move further in the checkout you loose the / or get the wrong ID :
/index.php/tickets?task=cart.add_cart&id=111&pt=123456
and then get a 500 error because apache gets no answer from the php-fpm ?
