Canvas LTI 1.3 upgrade issue

I'm hoping maybe someone has run into this and has found a solution. Otherwise, an FYI for anyone out there upgrading LTI 1.1 tools to 1.3 in Canvas.

Canvas seems to have an issue when upgrading an LTI 1.1 app to an LTI 1.3 one. I've only tested this on a course-level LTI 1.1 app, so don't know if it applies to site-level LTI 1.1 apps too.

These are the steps that led to the issue:
- Create a Canvas course that has a course-level LTI 1.1 "app", with several assignments that launch to that tool.  It doesn't seem to matter if the links have been ever clicked on or not.
- Install an LTI 1.3 developer key and "app" for the same tool.
- Delete the course-level LTI 1.3 "app" (though the LTI 1.3 config seems to override the course level LTI 1.1 tool anyway)
- Click on any of those LTI links.  Canvas returns a "Page Error", caused by a 500 error on the GET request to https://site.instructure.com/courses/###/assignments/###

Interestingly, editing the assignment and clicking "Save" without changing anything fixes the issue for that one link, and it will work properly after that.  But since that would require editing every assignment in the course, that's obviously not a great solution.