Can not execute event observer '\block_akna\observer\course_observer::module_viewed'

• line 164 of /public/lib/classes/event/manager.php: call to debugging()
• line 75 of /public/lib/classes/event/manager.php: call to core\event\manager::process_buffers()
• line 795 of /public/lib/classes/event/base.php: call to core\event\manager::dispatch()
• line 654 of /public/mod/feedback/classes/completion.php: call to core\event\base->trigger()
• line 70 of /public/mod/feedback/view.php: call to mod_feedback_completion->trigger_module_viewed()