If a vendor is assigned to other jobs with cross dates, the system will warn you about that when you press the "Start job" button.
The system will display the chart and list of assigned jobs with cross dates:
Here you can confirm the assignment by pressing "Confirm start job" or cancel it by pressing the "Cancel" button.
You can also change the deadline for this job or reassign it to another vendor by pressing the "Change vendor or dates" button.
To open the job that has already been assigned, click the job code or job name on the list: