H5P Course Presentation Save Fails

I have an Opigno 2.11 site on Pantheon.io. Whenever I go to create an H5P Presentation activity from within the 'New Training' workflow and click 'Next' after adding 1 slide with just a text box containing the word 'test', the AJAX cursor spins but the activity does not save. The 'Next' button is clickable again and upon clicking again it just repeats the issue. If I create the same activity by going to Opigno Module - > Activity List -> Add Activity > Interactive content and selecting 'Course Presentation', it either times out upon save or does nothing. No errors recorded in the Drupal logs. Anybody know why this is broken, creating the most basic presentation? I can create other H5P types ok.