I am using php 7.0 on several accounts and when NextGEN gallery plugin is Active, xmlrcp.php is blocked and Jetpack and the WP app both iOS and Android won’t work.
I rolled back to php5.6 just to try. It doesn’t matter which version for me. As soon as I deactivate NextGEN, all works properly.
While another gallery plugin might solve the issue, hundreds of posts who need to be edited and that is not practical. And so I would prefer using nexgen obviously.