Now i dont know if it will diagnose the problem but funny two gears have gone? Were they both in the same car? The reason i ask is i stripped clutch bell teeth on brand new clutch bells recently even though the mesh was good. After inspection i diagnosed the problem to be loose engine mount screws (the ones that hold the engine to the engine mount looking down one the car). There was just enough vertical play to cause a problem and strip teeth. Did not notice it until i stripped the engine right out? Maybe the same thing could be happening but instead effecting the spur rather than the clutch bell. I've always used the hotbodies spur. 2.5years and no problems with it. Got fed up with xray ones chipping/breaking. As i've not had a problem using the HB version i've never switched to the Xray updated ones?
Maybe it'll help to take a look but i know how irritating it is to strip a spur