When using multiple L-Server console screens (VMware vSphere 5.1 or later) to connect to the same guest OS device, later attempts to connect to the same guest OS device will fail. However, the message "In use on another console screen" is not displayed.
The connection status is not reflected in the device list when connecting to the same guest OS device. Wait a little while and then click the [Update] icon to obtain the latest connection status.