Same problem here, Gravity Forms 1.9.15 and latest Yoast SEO 3.0.7
Could not create new forms and removing input fields will result in an ajax error. Not all sites with this combination failed, some of them are still working fine. I had to revert to previous version of Yoast SEO 3.0.
We checked all other options like memory, themes and other plugins.
Thanks to Richard of Gravity Forms and the debug tool we found out Advanced Custom Fields was not the problem. This was our first guess…
