Failure to Submit to Next Step. If an employee and/or Union fails to submit written grievances to the next grievance step within the time limit so specified, it will be assumed that the grievant has dropped the grievance at that level. If the District at any step fails to respond within the required time limits, the grievance shall automatically move to the next step. However, the District and the Union may mutually agree to extend the time limits at anyone of the steps.