Having a similar issue. So, I just replaced my rear diff on my Kraton 6S EXB V2. 3 weeks later my rear, left tire does not spin when I give it throttle. I noticed fluid leaking out of the dogbone cup so I took the rear apart. I didn't see anything out of the ordinary… no gears stripped, grinding or anything. I put more diff fluid in it, put it back together and it still has the same problem. Only the front and rear right tires spin when I give it throttle. Could it be the center that's the issue? Any other issues you can think of?