Alright you were correct Elliot, it didn’t like being fired on init, and the other part of the problem seemed to be my use of the following filter along with the acf_add_options_sub_page()
add_filter( 'acf/options_page/settings', array( $this, 'acf_options_page_title' ) );
Not sure if this filter is now deprecated with the 1.1.0 updates or not but they didn’t play well together. Ended up just using the acf_set_options_page_title() and acf_add_options_sub_page() tags, not in init, and everything then works fine.
Thanks Elliot!
