If you are running Ultimaker Cura on a computer that has multiple microcontrollers, such as CNC and Arduino devices, you may notice your devices exhibiting unwanted behaviour. This is because Ultimaker Cura is set up to search for USB port connected devices at start-up. Furthermore, it may communicate with these devices in erroneous ways.
Note: This is not relevant for Ultimaker printers.
To prevent this behaviour you can disable the USB-plugin. Go to Marketplace - Installed - disable the USB printing plugin - restart Cura.
Note: When disabling the plugin you can't print over USB.