I’m not running any cache plugins, but the site is on WP Engine, which does cache the front-end aggressively. I didn’t know they cache on the back-end too.
I have a local copy of the site I’m working on and just checked – it looks like ACF is working as it should on the local site, but not on the WP Engine site. So I guess this might be a WP Engine issue, I’ll check in with them.
