Could not start executor. The handle is invalid (Exception from HRESULT: 0x80070006 (E_HANDLE)

Could not start executor. The handle is invalid. (Exception from HRESULT: 0x80070006 (E_HANDLE) When jobs are in a pending state, after completion of the current jobs when the pending jobs are trying to start they are getting faulted in the orchestrator.

The root cause for this issue has been captured in the Frequently Encountered Orchestrator Errors page.   

A. Projects containing UI Automation - when a RDP connection already exists in the background (minimized).
B. As a known Windows issue

Make sure all users are logged out when the session is about to be initiated from Robot.
For more information, refer to this forum post wherein the ‘Handle is invalid’ issue has been discussed. 

The process which is being executed should be scheduled at intervals with keeping in mind a gap of 1 or 2 minutes between two subsequent process. 
Avoid piling up all the schedules at a time.