Hi @floatingpoint
Could you please clarify that you updated the field from the backend or front end (using the acf_form() function).
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. This will make sure that no custom function prevents the saving process.
It’s also possible that you have reached the max_vars value of your server. Please check this page to learn more about it: https://www.advancedcustomfields.com/resources/limit-number-fields/.
If the issue persists, could you please open a new ticket here: https://support.advancedcustomfields.com/new-ticket? Please explain the issue again or provide the links to this thread. Also, please provide temporary admin credentials to your site in the ticket.
Thanks!
