Sharepoint Task Due Date updating on ALL Tasks when new members are added to permissions group

When adding a new member to a permissions group, the due date on EVERY task on our sharepoint task list adds one day to the due date and sends a notification that the task was updated.

This results in thousands of emails being sent out from task due dates being updated to our entire organization. Most of the tasks have already been closed out and are from years ago.

Any ideas on how to fix this or how to start troubleshooting? Our local team has tried to troubleshoot this error and hasn’t come up with anything.

Thanks!