Switch implements a mechanism for detecting and handling situations where two or more SwitchClient users would replace a job at the same time. This is important because it would be impossible to decide which replacement job is the "winner".
When a user clicks the Replace job button and Switch detects that another user is in the process of replacing the same job, SwitchClient displays an alert dialog with the message "User xxx is currently replacing this job; if you press the overrule button, the replacement job provided by user xxx will be lost".