Sign-coherence conjecture for principal coefficients

Let $B$ be an exchange matrix, and consider an extended exchange matrix in a $Y$-pattern with initial exchange matrix $B$ and principal coefficients. The rows indexed $n+1$ through $2n$ are the coefficient rows associated with the principal coefficients. Sign-coherence conjecture. For every such extended exchange matrix, rows $n+1$ through $2n$ form a sign-coherent set of vectors. This conjecture is known in many cases, including skew-symmetric exchange matrices and certain classes of non-skew-symmetric matrices, but is not known in full generality.