Thanks again @rmartin. You met two actual (rare) bugs.
The second, i.e.
Program received signal SIGFPE: Floating-point exception - erroneous arithmetic operation.
was due to a not initialized variable in a photonuclear reaction by … a relatively low energy muon (!),
while the first, i.e.
At line 63 of file preeq/xinpro.f Fortran runtime error: Index '113' of dimension 1 of array 'amssst' above upper bound of 100
comes from the pre-equilibrium de-excitation of a too heavy nucleus produced in a U ion reaction on tungsten.
The respective fixes, concerning only users who experienced these crashes, will be released with FLUKA 4.0.2 later this autumn (let us know at fluka.teamATcern.ch if the crash occurrence prevents you from waiting until then). Note also that, contrary to your suspicion, both issues were already affecting FLUKA 4.0.0 and the fact that you observed one of them only with FLUKA 4.0.1 is just a matter of random history.