Pruss has a good grasp of the quantum mechanical objection. He even presents a version of the famous EPR-Bell inequality paradox. He goes on to suggest several ways of reconciling QM with the PSR, including non-local causation, or backward-in-time causation, and hidden variable theories. With regard to the latter, he acknowledges that Bohmian theories run into problems with relativity, and are not a really satisfactory replacement for standard quantum field theory. But, he says, it is possible to show that some such theory could, in principle, explain the QM results.
For instance, take a neo-Leibnizian theory that says that every point of space is a monad, and this monad has encoded within it a list of all the events that will happen throughout time at that point and through an internal causal process it goes deterministically through these events as time passes.Now, it seems obvious to me that this solution achieves too much. For this could be said of any conceivable pattern of events in any conceivable universe. No matter how random, lawless, and chaotic, those events could be described in Pruss's monad theory as deterministic and causal. So this solution makes the PSR trivial, and therefore uninteresting. If every possible pattern of events satisfies the PSR, then the PSR has no content.
If the PSR means anything at all, then it needs a more rigorous notion of "reason" and "causality" than Pruss is employing here.