Cannot save units in CoursePress

On "mopa.wpressr.com" units in CP cannot be saved. Clicking on "Save whole units" return an error.

There are two errors in console reported (see screenshot) even though all the plugins on the sub-site and on the network are disabled.

Please note: it's a MultiNetwork multisite, the main site is ussunnah.org. wpressr.com is not yet live but it's a part of multinetwork so be very careful when dealing with FTP (install is for ussunnah.org as the "parent" of multinetwork - and it's live).

Credentials in chat.