I am currently using the eLearning module. I want to add a content item in a course where users can upload a file (e.g. pdf, jpg). So I used the webpage option when creating that content item and I added a form (the website editing snippet thing) to the page since it supports a file upload.

However, when I try to submit that form (whether with or without an attached file), it gives an error 'The form's specified model does not exist' next to the submit button. What's more confusing is that this problem does not happen when I test the form in the contact us page.
Any idea on what's causing this?