It's not limited to Keyclone. I'm full hardware and I do get "runaways".

Suvega and I have actually been able to consistently repro one cause:
If you are on auto-run, and someone stuns the "main", the /followers continue in the same vector direction without stopping, even though the main is "stunned".

Another logical cause:
You are moving around. You hold down a movement key (EVENT: KeyDown). The computer is waiting for a "KeyUp" event. You toggle repeater/multicasting "off". You release the key (EVENT: KeyUp), but only one character receives this message since broadcasting is off. The rest continue moving until they receive a "KeyUp" event.

Finally, hunters:
For some reason this class is my biggest "runner". It has something to do with when I stop moving and immediately begin casting (shooting) a "channeled" spell (steady shot follows your target). This did not happen much, if at all, pre-steady shot.