kvm usb switching is always broken, sometimes subtly, sometimes obvious

I use mechanical USB switches to individually switch USB lines like this:

https://www.amazon.com/dp/B01I0Y3GEE

one for keyboard, one for mouse

Problems it avoids

- cable speed usb

- no extra latency

- using boot-up hold-key-down sequences on macos works fine

- keyboard doesn't get hung in weird states

- no hotkey conflicts

- no mouse gets in weird state on one system that persists to another

etc etc etc