It’s WPML fault. In a website where I’m using ACF Pro 5.2.0 and WPML 3.1.8.6, this issue doesnt happen. So I suppose it’s with the new WPML version 3.1.9 that makes this problem come to life.
Instead of regressing to a previous version of ACF, try to regress to WPML 3.1.8.6 and report this issue to the WPML developers, also.
