HDL Error only one manager can be a line manager

Summary

When i try to Update Manager for an employee i get the error "only one manager can be a line manager". There is no future date track changes for the employee record

Content

Below is my HDL i uploaded which got into errors. When i try to update the Manager manually it goes fine. 

The Employee don't have any future dated record or any other special scenario. I used the same kind of HDL for manager updated and all went fine, also i used the same manager for few other employees and all went fine. 

Any reference to what could be the issue here.