I’m afraid I couldn’t reproduce this issue on my end. Could you please try to reproduce the issue on one of the WordPress’ stock themes (like Twenty Fifteen) with other plugins deactivated? If it disappears, then you can activate the theme and plugins one by one to see which one causes the issue.
I tried it on theme “Twenty Fifteen” and it works fine. On my custom made theme it doesn’t 🙁
Thing is, free version of ACF works just fine, and PRO version did work before WordPress upgrade… 🙁
I guess i’ll have to downgrade WordPress than.