PHP Fatal error: Uncaught Error: Call to undefined function submit_button()

Hello there,

i've an issue with automatic sync from WPMUDEV. Got error 500 when trying to auto-setup defender from WPMUDEV hub ... i'm not sure from where it comes, and on Google there is no good answer.
My WordPress installation is at its basic, fresh install. I've set what required to auto-install plugins by php7 libssh2 from the admin panel. WPMU Dashboard was auto successfully installed via Sync feature from WPMUDEV Hub. WordPress version is 4.8.1. I'm my own web provider (dedicated server) and use Apache2 with PHP7.0 (with userdir mod).

Here the error:
PHP Fatal error: Uncaught Error: Call to undefined function submit_button() in /home/MYUSER/public_html/WP/wp-admin/includes/file.php:1279\nStack trace:\n#0 /home/MYUSER/public_html/WP/wp-admin/includes/class-wp-upgrader-skin.php(95): request_filesystem_credentials('', 'ftpext', false, '/home/MYUSER...', Array, false)\n#1 /home/MYUSER/public_html/WP/wp-admin/includes/class-automatic-upgrader-skin.php(47): WP_Upgrader_Skin->request_filesystem_credentials(false, '/home/MYUSER...', false)\n#2 /home/MYUSER/public_html/WP/wp-admin/includes/class-wp-upgrader.php(196): Automatic_Upgrader_Skin->request_filesystem_credentials(false, '/home/MYUSER...', false)\n#3 /home/MYUSER/public_html/WP/wp-admin/includes/class-wp-upgrader.php(691): WP_Upgrader->fs_connect(Array)\n#4 /home/MYUSER/public_html/WP/wp-admin/includes/class-plugin-upgrader.php(110): WP_Upgrader->run(Array)\n#5 /home/MYUSER/public_html/WP/wp-content/plugins/wpmudev-up in /home/MYUSER/public_html/WP/wp-admin/includes/file.php on line 1279, referer: http://www.mywebsite.ca/wp-load.php?wpmudev-hub=5995...

Thank you so mutch for your support :slight_smile:.