Hello @bbennett2
Thank you for contacting the Canvas Community. We're sorry to hear you've been experiencing issues with Blueprint and Commons options. Thank you for explaining it in detail, I will do my best to answer your questions in the same order:
1. Once a module or item is locked, re-syncing it shouldn't cause any "exceptions" or issues. I'm not entirely sure what you meant by exceptions, but the locked content remains in place and teachers in the child courses wouldn't really be able to make any edits to that content. If you change it at the BP level and re-sync then those changes should display for your teachers:
https://community.canvaslms.com/t5/Admin-Guide/How-do-I-lock-course-objects-in-a-blueprint-course-as...
2. If you make updates to assignments after students have already submitted work- No their submissions remain and are not deleted or anything like that. The only issue would be if you deleted an assignment or student enrollments. You can change an assignment from 0 points file upload to 100 points, media entry only and every original submission would stay intact.
3. If you are updating Commons courses the teachers do not receive direct notifications that they have been updated. However, there have been many requests for this already and you should check out this page and also upvote this: https://community.canvaslms.com/t5/Idea-Conversations/Push-alert-notification-for-an-update-to-a-pag... We implement great ideas such as this that we find within the community. There are other ideas and options in that thread for commons notifications as well.
Hopefully this helps. If you have more specific questions, it may be best to speak with Canvas Support directly and/or even your CSM if needed.