I don't know why, but my OmniView Pro3's (16 port rack-mount) have all caused me problems. Usually with the keyboard being very non-responsive or slow, and sometimes the mouse and keyboard not being sent to the computer at all.
I think 90% of my issues began when we connected a Mac Mini to them, so perhaps there is some weird voltage difference, but even when we removed them we still can't get a reliable connection. We've changed to moving a keyboard mouse & monitor between computers when needed.
YMMV, and I've heard others say they love their OmniView KVMs.