CathInfo.com

Can't vote.  OUM is infallible on matters that are taught thereby to be "divinely revealed" (as per the VI definition).  But, as CE states, as a matter of practical judgment, it's not always possible to discern whether something has been taught infallibly by the OUM.

https://www.newadvent.org/cathen/07790a.htm

Quote

And while for subsequent ages down to our own day it continues to be theoretically true that the Church may, by the exercise of this ordinary teaching authority arrive at a final and infallible decision regarding doctrinal questions, it is true at the same time that in practice it may be impossible to prove conclusively that such unanimity as may exist has a strictly definitive value in any particular case, unless it has been embodied in a decree of an ecuмenical council, or in the ex cathedra teaching of the pope, or, at least, in some definite formula such as the Athanasian Creed. Hence, for practical purposes and in so far as the special question of infallibility is concerned, we may neglect the so called magisterium ordinarium ("ordinary magisterium") and confine our attention to ecuмenical councils and the pope.

Vatican II was an ecuмenical council approved by the pope.  But it had errors in its decrees.  Either the OUM is in error at Vatican II or the man who approved the errors wasn't pope.