So, this is definitely an issue with ACF 5.7.8. I will not perform update on other installations.
I will post an issue on the github of ACF. In general, do you know if they react quickly ?
For the downgrade, I suppose this is only possible if there was no change in the database structure. And to do so, you simply replace the files in wp-content/plugins/advanced-custom-fields-pro ?
Thank you.
