Hi James,
Thank you very much for the detailed response. Again, we are having very similar experience. We just heard back from Canvas Engineers that the issue has been resolved for FUTURE New Quizzes sync but for the existing New Quizzes that are not synced well or had errors like no content in them (just like quizzes with no questions in them in your case) will have to be fixed manually. We have about 100 associate courses or more cumulatively which we need to go in and make manual fixes for the multiple New Quizzes within those courses. We are discussing our options with Canvas team to work on the solution without any unwanted repercussions. They have provided us with two options so far: One to use course export tool and Second is the course reset option both of which are very manual processes and simply too time consuming.
I am new to the API world and have not used it. Having said that I understand the overall process you've undertaken to monitor the issue and would like to make a guess here that since NQ still operate a bit on the external tool side of the Canvas interface, the BP sync shows that the sync is complete when the New Quizzes '"shells" are created and then it lets the external app make copies inside the "shells" after the Sync process has finished from the BP course. i.e., the sync progress bar coming to a stop and the BP course registers that the sync is complete.
While this copy is happening, any changes made to the NQ such as editing it from the Modules page or hitting of "retry" or "cancel" button affects the quiz by breaking its link (probably treats the NQ as an edited Quiz) and prevents it from receiving further updates or finish the copy process.
I found that the while the NQ were getting synced, teachers of the associate course or admins had the opportunity to click on any of the NQ from Modules page. If they did that, (I tested this too) the Quiz will appear to have just the title and no content or questions in them. This opening/editing of a New Quiz from the Modules page also prevents it from getting the content copied across from the blueprints and somehow breaks the link. Which would then also prevent it from receiving further updates from future course syncs and gets listed in 'Exceptions'.
I am now thinking in the direction of how to fix the existing NQs that are in error state if Canvas does not come up with a time saving fix rather than manual individual associate course fixes. I'll update here if I come up with a better solution or if Canvas provides a good workaround.