Whatever issue you are having that issue is going to be with the import plugin you are using and not with ACF.
There are some specific things that could be causing the issues that you are describing.
The fist is that the other plugin is not saving the correct acf field key reference in the database. The field key reference is saved with a meta key that matches the field name and is prefixed with an undersore (_) "_{$field_name}" and the value of this field is the field key of the associated ACF field.
ACF expects each meta key to have exactly one entry in the database. Saving but reverting to a previous value is a symptom of having multiple entries in the database for the user with the same meta key.
Another cause of saving an reverting to some other value can be the existence of multiple fields with the same name (meta_key). ACF field names must be unique.
