accordions not working in backend anymore

I can\'t edit my accordions anymore (in backend). I see only the tabs of accordions options but no reaction when clicking them.
Here\'s the error code by wordpress:

Fehler-Details
==============
Ein Fehler vom Typ E_ERROR wurde in der Zeile 349 der Datei /usr/local/vhosts/partnerschaft/www/wp-content/plugins/accordions/includes/meta.php verursacht. Fehlermeldung: Uncaught Error: Undefined constant \"post_grid_textdomain\" in /usr/local/vhosts/partnerschaft/www/wp-content/plugins/accordions/includes/meta.php:349
Stack trace:
#0 /wp-admin/includes/template.php(1409): meta_boxes_accordions_input()
#1 /wp-admin/edit-form-advanced.php(711): do_meta_boxes()
#2 /wp-admin/post.php(206): require(\'...\')
#3 {main}
thrown