Some users don't get Team Calendars event email notifications

[Codeworx 3]

We have some shared calendars that everyone is meant to get an email when they are updated (events added, removed, updated), but not all users receive them, everyone has subscribed and set to watch the calendars, some users just don't get the email notifications (they are not appearing in the confluence mail queue, so it's not the mail server stopping it).

I've poked around the AO_950DC3_TC_SUBCALS table but the referencing method is confusing (only read, have not written to the table)

Is there a method to check in the database if a users should receive an notification from a specific calendar ?

[Codeworx 3]

I ended up recreating the calendars (export, delete, import) individually and it seems to have worked, but I won't know for sure for a few weeks (the time it takes everyone subscribed to resubscribe)