User in Invoice Workflow able to approve transaction twice?

One of our departments has a specific workflow for how invoices flow through approvals. When User X submits an invoice it should go to the following path:

Approver 1, Approver 2, Approver 3, Approver 4

The issue we are having with this workflow is that once Approver 1 clicks on "Approve" for the invoice, the notification does not leave their notification bell. And if Approver 1 opens the notification again, after approving their step, they're able to click approve a second time. This does not give any error or anything, and is basically bypassing Approver 2.

When other users in this workflow do their approvals, the notification clears from their bell immediately, but this does not happen for Approver 1. Why does the notification not clear after Approver 1 clicks approve? Or alternatively, why is Approver 1 not receiving an error when clicking "Approve" a second time?