WordPress 4.4 is introducing a breaking change related to the show_ui argument of the register_post_type() function. While it is a breaking change, it is an overly positive change as well because it corrects previously unexpected behavior with post types that are registered with the show_ui parameter set to false.
This change does, however, have a negative impact on our Frontend Submissions extension. In FES version 2.2.17 and earlier, the fes-forms post type was registered with show_ui set to false. Because of this, the form builder pages in FES 2.2.17 and earlier will no longer behave as expected. When attempting to access the form builders on WordPress 4.4 and greater, the following error message will be shown:
To resolve this issue, simply update to Frontend Submissions version 2.3 or later.
For users that are unable to update to FES 2.3 or later, the following patch may be applied to resolve the issue:
It should be noted, however, that we strongly advise against using this patch as a solution. The best way to resolve the issue is to update to 2.3 or later so that new features, bug fixes, and security updates can be applied as well. This patch should only be used as a last resort.