Hi Polly Robinson,
The locked/unlocked state of objects in a Blueprint site is different from published/unpublished state. Take a look at this screen grab from one of my testing sites:

Blueprint courses have an extra icon right next to the published icon -- it looks like a stack of papers (or "blueprints"). Items that are "locked" have a padlock in the center; items that are unlocked do not. See the examples called out in the screen shot above. Though this is from the Blueprint parent site, these icons are visible in both parent and child sites.
In the screen shots that you shared, everything looks to be unlocked. That is what I was referring when I said that it looks like everything in the Blueprint parent site is unlocked.
And this is important, because it's directly related to the Blueprint sync exceptions that you have seen.
Unlocked items in Blueprint courses can be changed, and those changes will not be overwritten by later changes made to the parent site. When a change is not propagated across the child sites, a sync exception occurs. Canvas assumes that the teacher in the child site changed an unlocked item for a reason, so it lets those changes stand.
When there's content that you don't want to be changed within the child sites, you should make make sure to lock each item. (See How do I lock course objects in a blueprint course as an instructor? for more information.) Unfortunately, the contents of Blueprint courses aren't locked automatically and have to be locked individually -- though there's a feature idea you can vote on (https://community.canvaslms.com/ideas/11932-lock-all-content-in-blueprint ). (The locked attributes on Settings > Course Details just specifies which attributes should be locked when an item is designated as "locked.")
So -- if you changed something in the assignments in the child sites (for instance, changed the due dates/times), then this would cause a sync exception because once you change one unlocked or unlockable attribute in a child site, you disrupt the ability to sync any unlocked/unlocked attribute of that object via a course sync.
Depending on what changes you are trying to propagate (changes to the content, for instance), you may be able to just lock the item in the parent site and then sync. Once the item is locked, then the locked attributes (whatever you have designated from among content, points, due dates, and availability dates) in the parent site will override the changes made within the child site.
I hope this helps explain what's going on. Good luck!
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