The problem seems to be the specification
occbin_constraints;
name 'leverage'; bind mult>0; relax mult<0;
end;
which means mult=0 is none of the regimes. This type of setup makes it hard to figure out in which regime the simulation is. Usually, one includes more of a buffer between the two regime as in Occbin: "increase maxit or check_ahead_periods" with very high maxit and check_ahead_periods - #7 by jpfeifer