I can't speak to the issue with grading periods, but I have a recommendation about bringing content from the old course into the new course. Rather than "copy" items, I would highly recommend "importing" them. Here's the Canvas guide:
https://community.canvaslms.com/t5/Instructor-Guide/How-do-I-copy-content-from-another-Canvas-course...
A few important points:
- Unless you want everything including old Calendar Events and Announcements, always go with "select content." I teach semester-long courses, and I import the Modules and the Syllabus. When you import the Modules, everything in the Modules will automatically come over.
- Always, always, always choose the option "adjust events and due dates." Then I highly recommend that you "remove" the dates altogether. You can also "shift" dates, but this has never worked well for me.
What you're doing now - "copying" the items and changing the dates - is creating a lot of unnecessary work for yourself.
Finally, I always "import" the course content before the new semester starts so that I can unpublish everything before the students have access to my course.
***NOTE TO CANVAS DEVELOPERS**** You would save instructors so much time and energy by automatically making all of the imported items "unpublished." When everything comes over as "published," it's like "death of a 1,000 clicks." it really is.
***I know that many folks have already proposed this in the Idea Conversations. Maybe it's time to just fix the issue. Just saying. 🤔