I've recently migrated my wordpress multisite on to a new server that is running php7.2. I had to because most of the plugins I was using were no longer supporting php5.5.9.
On the old server, I created a plugin for each of the sites within the multisite that adds a custom post type with additional meta boxes. These no longer work but that's beside the point.
My problem is that I've installed mb custom post type to try and recreate these plugins. Mb custom post type appears in the dashboard but when I click on it and try to add a new custom post type there are no boxes to fill in. Then, if I press publish the whole site crashes and I have to uninstall it again. Please help!