I have a workflow that involves 4 employees. The first employee will submit the workflow and employees 2 - 4 will approve, reject, or ask a revision one by one according to position from lowest to highest (supervisor > vice head > head).

It was going so well until this error popped up. I checked all the destination for the tasks and all the decisions. I also tried deleting the tasks one by one in a dummy copy but nothing seems to work.