Canvas makes jQueryUI widgets out of rich content that has the following class names: .dialogue, .draggable, .resizable, .sortable, .accordion, .tabs.
Canvas is moving away from jQueryUI for their own widgets and this behaviour will go away. As announced in Canvas Production Release Notes (2017-06-24), accordion widgets are no longer supported as a jQueryUI component.
While planning your course content for 2018 offerings, do keep in mind, UI widgets listed above will no longer be available, at various points through the year. Please refrain from making use of these in your course resources.
The temporary fix for accordions that has been put in place this year to allow for courses to complete their course delivery, will no longer be available next year as it has a detrimental effect across the load time of all courses in Canvas, regardless of the function being used.
Read more on Canvas community: