I have 6368 280kv motor. It was going well but something got stuck in the motor so I had to disassemble it. After I assembled it back, motor started to vibrate vigorously at high rpm. I have realised that the motor part where it rotates is slightly off centre. As you can see, the gap is bigger on one side than the other.
Looks like your shaft is bent. Just buy a new shaft and replace it.