Changing types of fields in attributes might result in incompatibles types and existing objects being unable to be migrated.
When this happens, IRIS will not update the fields of these objects and let them as is to prevent any data loss.
This behavior can however be changed by using the Complete overwrite and Partial overwrite buttons.
Partial overwrite basically resets the attributes values of every {{ attribute.attribute_display_name }} objects that matches the current ones, and then applies the current attributes.
All associated values are lost. This does not impact attributes pushed by modules.
Complete overwrite resets all attributes of every {{ attribute.attribute_display_name }} objects, including the ones created by modules, and then applies the current attributes.
All associated values are lost.
In any case, none of the native values of the {{ attribute.attribute_display_name }} objects are modified. This only concerns custom attributes.