Missing merge conflicts email notification

I have a large MR where I split it up into smaller MRs (!20521 (merged)).

I made changes to the other MRs and they got merged to master so I know there are conflicts.

The UI also shows that there are merge conflicts but I never got the email notification.

This has happened to me several times already and I'm not sure why. I cannot reproduce with GDK locally.

I've also asked in Slack and others seem to have the same problem too.

I'm not missing any other notification emails, just for merge conflicts, so this seems odd.