Frontend Editing: K2Notify returns error when editing notifications are on

[PhilippSPOTTERON]

When notify on edit is active, the plugin returns an error in Frontend editing after hitting save:

Whoops \ Exception \ ErrorException (E_COMPILE_ERROR)
require_once(): Failed opening required '/var/www/vhosts/schweizforscht.ch/httpdocs/administrator/components/com_k2/lib/JSON.php' (include_path='.:/opt/plesk/php/7.3/share/pear')
COPY HIDE
Stack frames (4)
3
Whoops\Exception\ErrorException
/var/www/vhosts/schweizforscht.ch/httpdocs/plugins/k2/k2notifyadmin/k2notifyadmin.php424

[PhilippSPOTTERON]

Seems the issue occurs when the K2 form is open in a modal box.
(now also with creating new items, sadly > plugin seems broken)

[PhilippSPOTTERON]