Almost all the issues I've read about regarding Ferris seems to stem from lack of maintenance. I truly believe that many owners don't know how to use a grease gun, change oils, especially changing the HST drive oil at least every two years. Wheel bearings? Probably never greased them...
I had the same problem early on. I now have 450 hours on it with Kawasaki engine. i thought I was about to throw a rod by the sound. It was the engine mounting bolts. I checked and tightened the bolts to never have trouble again with that. Did burn out a pully but easily replaced that with...