  The existence of two metrics in massive gravity theories in principle allows
solutions where there are singularities in new scalar invariants jointly
constructed from them. These configurations occur when the two metrics differ
substantially from each other, as in black hole and cosmological solutions. The
simplest class of such singularities are determinant singularities. We
investigate whether the dynamics of bimetric massive gravity -- where the
second metric is allowed to evolve jointly with the spacetime metric -- can
avoid these singularities. We investigate whether the dynamics of bimetric
massive gravity, where the second metric is allowed to evolve jointly with the
spacetime metric, averts the simplest class of such singularities, namely
determinant singularities. We show that it is still possible to specify
non-singular initial conditions that evolve to a determinant singularity.
Determinant singularities are a feature of massive gravity of both fixed and
dynamical metric type.
