I was offered a PIP once. It was purportedly due to poor performance, but it was clear that I was being gotten rid of for other, non performance-related reasons. The actual goal I was meant to meet was unachievable because I was simultaneously throttled in the amount of work I was allowed to take on at once.

The whole place was a clown show that I was unhappy at anyway, so while I entertained the idea of taking them to court, when I realized the PIP is basically an elaborate attempt to defend against wrongful termination cases I ultimately just found a much better job.