I was thinking about the spontaneous appearance of particle anti-particle pairs in a vacuum. Can you say conditions x, y, and z are responsible for those particles appearing at that instant and there's no other way it could have gone?
Particle/anti-particle pairs don't really "pop into existence" in any meaningful sense, so probably not the best example of randomness.
We do see unpredictable effects (randomness) quite often, though. Bell's theorem provides some constrains on their source.
But for one to exercise free will (selection of one of multiple future states from a given present state) to, say, not eat the last oreo by biasing quantum randomness to invoke a whole chain of high-gain non-linear effects (maybe have a sodium ion change it's momentum slightly to cause a neuron to trigger to... etc etc... to send different actuation commands to the muscles to pick up the cookie) would require not just a mechanism for this free-will biasing but also retrocausality to let something in the system "know" that this was the place in its orbital where the electron had to interact in order to choose to leave the cookie until tomorrow. The use of a high-gain effect chain means that the initial instance of free will is smaller, and therefore more likely that we've just not noticed it so far, but it makes it harder to put together a meaningful story for how these free will instances reflect a "choice" instead of just a statistical divergence.
But an observation contradicting it would be the biggest discovery in physics in at least a century.