Ahhah! When I turned on debug mode I got back an error in the AJAX for ACF regarding Relevanssi. Here’s the related errors (I believe I have them all, but reading xdebug in the response field is a pain).
Notice: Undefined index: post_type in /media/sf_web/wp0/wp-content/plugins/relevanssi/lib/search.php
Notice: Undefined index: s in /wp-content/plugins/relevanssi/lib/search.php
Notice: Undefined index: posts_per_page in /wp-content/plugins/relevanssi/lib/search.php
Notice: Undefined index: paged in /wp-content/plugins/relevanssi/lib/search.php
If I disable Relevanssi, the relationship fields are working as expected, but I rather need Relevanssi to uh, search through all these lovely custom fields I’m making, and it’s currently working just fine with both of them enabled with the last version of ACF. 🙁
