I am also having problems with this. I de-activated plugins one-by-one, cleared all caches, and still I can’t save updates to a Course. The problem happens only when I use the course outline block. I can save a course without the block in the course (but then no lessons display on the course page so that is not a viable workaround).
With thanks
Laura
Perhaps some of the following is helpful….?
2021-01-03T17:42:10+00:00 CRITICAL Uncaught TypeError: Argument 1 passed to Sensei_Course_Structure::instance() must be of the type int, null given, called in /var/www/wp-content/plugins/sensei-lms/includes/blocks/class-sensei-course-outline-block.php on line 190 and defined in /var/www/wp-content/plugins/sensei-lms/includes/class-sensei-course-structure.php:41
Stack trace:
#0 /var/www/wp-content/plugins/sensei-lms/includes/blocks/class-sensei-course-outline-block.php(190): Sensei_Course_Structure::instance(NULL)
#1 /var/www/wp-content/plugins/sensei-lms/includes/blocks/class-sensei-course-outline-block.php(260): Sensei_Course_Outline_Block->get_block_structure()
#2 /var/www/wp-includes/class-wp-block.php(221): Sensei_Course_Outline_Block->render_course_outline_block(Array, ‘\n\n’, Object(WP_Block))
#3 /var/www/wp-includes/blocks.php(722): WP_Block->render()
#4 /var/www/wp-includes/blocks.php(760): render_block(Array)
#5 /var/www/wp-includes/class-wp-hook.php(287): do_blocks(‘<!– wp:paragra…’)
#6 /var/www/wp-includes/plugin.php(212): WP_Hoo in /var/www/wp-content/plugins/sensei-lms/includes/class-sensei-course-structure.php on line 41
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