ACF is limiting me to only 52 fields in a single field group. When I try and add any more they don’t stick when saved. Is this correct or broke?
You are running into php_max_input_vars
. In order to save more fields you will need to increase the value of this setting. This plugin is helpful for detecting the problem https://wordpress.org/plugins/wp-max-submit-protect/, but the only place it can be changed is on the server.