Review on TNP 16-Port USB 2.0 KVM Switch with Manual Selector, Rack Mount Metal Box Adapter and 16 VGA USB KVM Cables for Computer PC Laptop Notebook Server Monitor, Keyboard, Mouse - Black by Kevin Robinson

USB ports aren't getting enough power. USB mice aren't power hungry enough for that, but some USB keyboards are hungry. Unfortunately, this includes clickable M models; Results range from a keyboard that won't initialize at all, to looping when trying to initialize and failing halfway, to borderline running and crashing when actively moving the mouse. Plugging a powered USB hub between the USB port on the KVM and the keyboard gets the damn thing working, but it would be much more convenient if the KVM itself had an additional external power supply.