If the Xiaomi Curved Gaming Monitor G34WQi shows black borders randomly, it often happens when switching display devices or using a new monitor. This occurs due to a mismatch between the monitor's native resolution and the current display settings. To resolve this, adjust the resolution settings to match the monitor's native resolution, which is 3440 x 1440. This will ensure that the image fills the entire screen without any black borders. Access the display settings and select the recommended resolution for the monitor.
If the problem persists, verify that the monitor's settings are correctly configured and that all cables and connections are secure.