Then Christianity crumbles from failure of its own structure.
Whatever the limits of the Truth, it must be self-consistent within; by definition and its own teaching, anything not consistent with the Truth isn't.
Tradition has proven itself inconsistent too often to be presumed correct from mere declaratory inclusion. That leaves Scripture as the only well-delineated bastion of Truth, whether or additional truth is contained therein. If inconsistencies - real ones, not perceived as such by sinful flawed minds - are found, they must be excised. The exercise has left us with the book we have; should more be removed, we have but dust left.
If that structure is sola scriptura, yes - for certain "One Lord, one faith, one baptism" cannot exist with it.
However if the well-delineated bastion is the pillar and foundation of the truth - which is the church of the living God founded and headed by Christ and led by the Holy Spirit, then it does not, and has not, crumbled and the gates of hades shall not prevail against it.