Planner tickets don't update name or assigned contacts

Dear All,

Our company is trying to use MS Planner for an overview of all projects in different phases. We realized, that not every assigned contact is getting e-mail notifications about the comments.
It seems, that a name change, or new/deleted assigned contacts on the ticket are not updated in the system. Still getting notifications with an old name, already deleted participants will be notified, but new ones will not.
Found some similar issues, has anyone else noticed? Is there any solution?