Modern Catholic ecclesiology (for example, in the CDF documents Communionis notio and Dominus Iesus issued when Joseph Ratzinger was Cardinal Prefect) considers a 'Church' to be a local body consisting of Bishop, Presbyterium, deacons , and people [er .. what about Abbacies nullius? But we'll let that pass]. Such a body ought to be in communion with the Holy See, but, if it isn't, it's still a true 'particular church', although 'wounded' by its lack of communion with Rome.
It is, of course, possible for a particular church to have elements of disorder within it. Few Christian ages or places have been entirely free of disorder. But how much disorder disqualifies an ecclesial body from being a 'particular church'? In the Anglican diocese of Barchester, for example, half the 'presbyters' are women purporting to be in holy orders. Obviously such a very large degree of corruption means that the diocese of Barchester cannot be in any real sense a 'particular church' and thus a local manifestation of the Church Catholic. So, the Bishop of Barchester, although a legal office-holder in the quaint old Tudoresque legal establishment, is not the Bishop of a 'particular church', and does not have canonical jurisdiction. Barchester Catholics will in fact be sedevacantists. This means, of course, that 'oaths of canonical obedience' are sworn to a vacuum.
But just how dysfunctionally corrupt does a 'church' have to be to lose its status? How structurally decadent does a 'diocese' have to be before it is reasonable to deem the episcopal tenure of its 'diocesan' a nullity?