It is clear that Schneider is desperately trying to find historical precedent for the Catholic Church teaching error so that he can sustain his position that Vatican II taught error but was nevertheless a legitimate ecumenical council promulgated by a valid Pope (“Saint” Paul VI). His careful caveat that such magisterial error is “rare”, cannot help him any, for that would make no difference in kind, only in degree (frequency); and in any case, error is certainly not rare in the magisterium of the Novus Ordo Church.
Final Remarks
The objective of this post has not been to settle the controversy about the Decree for the Armenians. Only the Church herself could settle it, and she has not done so. Rather, the goal has been to refute “Bp.” Schneider’s claims that the Council of Florence taught error, that Pope Pius XII corrected it, and that this serves as historical precedent allowing one to hold Vatican II to be legitimate but erroneous and subject to correction by a subsequent Pope.
https://novusordowatch.org/2020/06/athanasius-schneider-council-of-florence-holy-orders/