The only link I may imagine, classic mechanics is too deterministic to explain free will. Quantum mechanics, on the other side, has uncertainty as its fundamental principle.
There are many non-quantum phenomena which can't be accurately predicted, like turbulence and the stock market. I've never understood why the argument that 'it'a unpredictable, and therefore must be quantum' only seems to be applied to the brain.
Is free will not understood? I haven't seen a human make a decision in 25 years that wasn't based exactly on their prime motivations.
That's no more meaningful than saying "I haven't seen a particle behave in 25 years that wasn't based exactly on the laws of physics"