ACF field translation preferences may be ignored when fields used in custom blocks

Overview of the issue

A custom block may have ACF Field Groups assigned to it, where individual fields will have translation preferences. In some circumstances these may not be respected, and—for example—the value of a field set to Copy may still show up in the translation editor.

This can occur with Cloned fields, and will occur with fields added to a Group field.

Workaround

With Cloned fields there is a setting “Prefix field names”, which by default is Off. In that case the problem does not occur.

With Group fields there is no such setting, and until this is resolved fields should be structured so as to avoid using Groups.