  A new scenario for gravitational collapse has been recently proposed by
Haggard and Rovelli. Presenting the model under the name of black hole
fireworks, they claim that the accumulation of quantum gravitational effects
outside the horizon can cause the tunneling of geometry from a black hole to a
white hole, allowing a bounce of the collapsing star which can eventually go
back to infinity. In this paper we discuss the instabilities of this model and
propose a simple minimal modification which eliminates them, as well as other
related instabilities discussed in the literature. The new scenario is a
time-asymmetric version of the original model with a time-scale for the final
explosion that is shorter than m log m in Planck units. Our analysis highlights
the importance of irreversibility in gravitational collapse which, in turn,
uncovers important issues that cannot be addressed in detail without a full
quantum gravity treatment.
