I've had a lot of trouble with servo jitter lately, I seem so have solved the problem but I'm not sure why it has worked.
At first I thought it was the power supply being spiked, no amount of decoupling capacitors solved the problem.
I thought it was software and although my code was improved, the jitter continued.
Because I was using optic sensors, I thought fluctuations in the light is causing my inputs to give false readings. Still no luck and I stubbed my toe in the dark.