Andreatta–Wiśniewski fiber normality conjecture

Let $\varphi:X\rightarrow Z$ be a Fano–Mori contraction of a manifold of dimension at most $4$. Andreatta–Wiśniewski's conjecture. All fibers are normal, with the exception described in (3.6) of the cited work. The source states that, after subsequent results, the conjecture remains open only for birational Fano–Mori contractions of smooth fourfolds contracting an irreducible divisor to a point.