I've been flying the Rave pretty much from day one. I never had any interest in an electric or a small Heli. But I took a punt and love my Rave to death. But it took me a good 12 months to truely connect with it, how to build / replace bits correctly. I would over tighten screws and broke heaps! Of heads of screws. Would use too much locktite. The hardest lesson was learning to set the gear mesh. Yes, the lads have brought out the stronger black ones for the torque tube gearbox but even then I stripped a set as the mesh I set was too loose. Going tight is just as bad as the will eat each other and you'll lose power through unessacery ( can't spell) friction.
I replaced my head block reacently as i stripped a thread that one of the top mixing arms went into. In doing so, I ended up replacing all ball links and clips. About 200 flights. Think of the stress that poor head block goes through. The Rave is just so responsive and this puts more stress on bits. I'm not for a second saying 'expect parts to wear out' but if you fly hardcore 3d and have racked up a few flights and some good crashes, it might simply be time. Interestingly on head blocks, I was tweaking my 90 and the two vertical pins at the bottom of the head block ( which used to be the phasing ring) were not perfectly vertical and therefore when the washout base was going up and down it was not smooth. This maybe something you could investigate. Yes, the damage is done but at least you might find out the cause. I know I have offered no solution... My suggestion would be to replace the block and the main - hardened - shaft for a fresh start. Very very unlikely it's new and faulty.
Vibe 90 & 50 WITH flybars (old skool), CY Rave, flying for many years, talent rating, absolute zero