kneetarg unstable and general rigging query

Can you take a look at this file/rig please?
The kneeTarget jerks around whilst animating it, and I’m wondering if you can think of ways to improve the rig to helps this, and just point out any flaws in general. Thanks for looking.
(ps the character is for game development)

Sorry. Reparenting the knee targets to the Master bone seems to have sorted this. Must be some kind of cyclic thing.