We found an issue with the Elgo 160 landing system used on the early version Motion 4000s. We started to have intermittent governor trips (about once every 2 months) and had checked typical speed feedback devices (tach, couplers, etc...). It turns out that the primary speed feedback is through the Elgo so any unusual wear on the magnetic tape or tape guides can cause an overspeed issue. The new style Elgo 240 has a nylon liner that seems to protect the magnetic tape better and should reduce related issues. If your having intermittent overspeed issues on the Motion 4000 check for wear marks on your Magnetic tape.