Stubborn and Pax believe that 99.5% of the Magisterium (the non-infallible portion) can become corrupted with error at any given time.
No, I believe that 99.5% of the time, in the post-V2 period, the hierarchy has not made use of the Ordinary/Universal Magisterium because they haven't taught in accordance with Tradition. They have only made use of their fallible, ordinary magisterium, (i.e. they have taught as private theologians, mere bishops, etc).
The ordinary magisterium is not infallible in any way.
This notion that something also has to be universal in time has the corollary of suggesting that the entire Ecclesia Docens can fall into error on a significant point of Catholic doctrine, i.e. that the Magsterium can defect at any given time.
The hierarchy can fall into error, just like most did during the Arian heresy. St Paul/Scripture says that ANYONE can preach something different than what he taught and they should be anathema (i.e. that all teachings, post St Paul must agree with St Paul/Scripture). Ergo, yes, Church teaching is constant and universal, and that means a universal of "time". Truth is eternal, just like God is eternal. Church teachings are eternal and do not change. Your definition of "universal" is wrong.