Redmine

Environment:
Redmine version 5.0.2.stable
Ruby version 3.0.2-p107 (2021-07-07) [x86_64-linux-gnu]
Rails version 6.1.6

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Hello everyone.

We currently had the issue, that we had to review a bunch of older issues/tickets to check for relevancy or closing them.
When you edit the issue, you have the check box for suppressing email-notifications.
We assumed, checking this box will always silently submit the changes made to the issue, without sending a notification.

But several times notifications were send!

I'm admnistrator in our redmine with the settings in my profile to always get notified about all events in all my projects and i'm a member of all projects, so i naturally do get notified.

But my coworker, who did all these tasks and was the assignee, did not.
All watcher's did get notified.
The ticket/issue owner/creator got notified.

Why does the suppression check box not work?
Why do watcher's always get notified?

Are there any options in redmine to adjust this behaviour and make it more granular?
Is there a way to actually control, when the check box to suppress notifications is set, that nobody got a message?

We'd also sometimes need to update older issues, yet the project is done and finished for the customer, but to have some sort of documentation we add informations to the tickets. Like adding older mails or files and such.

We'd like to do this, without creating spam for our involved customers (issue owner, watchers).

Is it true, watchers and issue creators/owners "always" get notified and there is no way to control that?

Any tips, hints and pointers appreciated.

Thank you.