It’s WPML fault. In a website where I’m using ACF Pro 5.2.0 and WPML 18.104.22.168, 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 22.214.171.124 and report this issue to the WPML developers, also.
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