Unable to edit/save CoursePress units.

In CoursePress admin, when I try to edit any course Units, or add new ones, they will not save at all. It says it has saved, but on refreshing the page, the units are no longer there.

Error log throws up the following:

PHP Warning: Invalid argument supplied for foreach() in /hermes/bosnacweb01/bosnacweb01af/b2531/ipw.pestnetw/public_html/stage/wp-content/plugins/coursepress/2.0/admin/controller/class-unit.php on line 383