ACTION REQUIRED notification still appears on the bell icon of the approver for weeks

The approver has approved the approval notification and the invoice is now pending with other approver in the workflow. The Action required notification still appears on the approvers screen as if the action is pending with him. The "Synchronize Notifications in Global Header" runs in every 30 mins, but the notification and count 1 still appears on the screen. The user clicked dismiss all but again it still appears.

The user should not see the notification in his bell icon if he has already performed his action.

Can someone please suggest a workaround or is this a bug, that if the invoice is not completely approved the previous approvers still see the notification?