DIAGNOSIS The KVM firmware is losing the USB device handshake. This is often caused by peripheral power draw or incompatible USB peripherals.
FIX Connect your keyboard and mouse directly to the monitor's USB downstream ports. Do not use an unpowered USB hub between the monitor and your peripherals. In the OSD, go to System -> USB Hub and set it to 'Always On'. Re-initialize the KVM by switching sources using the dedicated 'PIP/PBP' button, not just the source menu.
IF THAT DIDN'T WORK Update the monitor's firmware. KVM stability improvements are common in firmware updates. Also, try different USB ports on the monitor. Some peripherals, especially high-draw gaming mice, can be problematic.
HEADS UP The KVM is designed for standard HID devices like keyboards and mice. Webcams, audio interfaces, or high-speed storage drives may not work reliably through it.