Editing the progress bar in large courses.

My course has slightly more than 300 trackable items and it seems I have reached a limit to using the progress bar. Somewhere around 315 items it worked fine (albeit slow) and then I added another activity and am now unable to edit the progress bar. If I delete an assignment, the progress bar becomes editable. If I add an assignment, it goes to the edit page but doesn't load. Have I reached a course limit?