Yip, had the same thing happen in a R44 Raven 1 a few years ago. After initial rev runaway, the governor continued hunting, and I turned it off and flew RPM manually back to base. All OK in cruise but not nice once you start changing power settings and trying to control RPM in the hover. I was spoilt by never having the opportunity to fly anything other than machines with governors, probably old news to the more senior pilots out there, so once that governor is gone, it is sorely missed. Turned out to be the governor control unit itself. From then on, no assumptions, check the needles as they go up, as in a turbine start.