Free will and the necessary evil

[Jehanne]

If the PSR can, in some instances, lead to erroneous conclusions, how can we have confidence in it?

Can you point me to a case in which reliance on the PSR led to an erroneous conclusion? 

As I understand it, the PSR only posits that everything must have a reason for why they are that way. How we find the reason, what we conclude the reason to be, whether we are right or wrong about it, are not a result of the PSR. Even if you believe in a strict version of the PSR, it's still entirely possible to say that we don't know what the reason is, and in fact humans may never know it.

Some of the conclusions of Aristotle, which he based upon the PSR, are false. Again, if the PSR is fallible, but neither testable nor falsifiable, why and how can we trust it?