I completely understand, @tyler_clair.
I cannot speak to what happened and why it happend but can provide ways for helping to alter email addresses that exist in Canvas.
You can using the "Provisioning" and "SIS Export" report that are available for each (sub)account. When doing that, request the "Users CSV" file to download and select the desired term(s).
After downloading the file(s), you can review the email address that exist and find anything that does not follow your institution's format.
You would then find the correct email address(es), manually create a users.csv file to upload or create a script for an API call, and upload the CSV file or "put" the API call.
If you had not already thought about these steps, I hope this helps you out.
-Doug