plugin nested pages overrides all fields of post_modified after new sorted

I am use the plugin "neted pages" and when I re-arrange (new order) the posts, then all fields "post_modified" (last modified) in my database have the same date (e. g.: 2016-05-11). This is not correct, then I have not changed the content, only the navigation structure. Have you a good idea? Please help me. Thanks.

Best regards

via Chebli Mohamed