more searching for the bug: narrowing it down

src/binary_c_maths.h

src/disc/disc_bisection_rooter.c

src/disc/disc_calc_disc_structure.c

src/disc/disc_constraints.h

src/disc/disc_logging.c

src/disc/disc_monotonic_check.c

src/disc/disc_new_zone_list.c

src/disc/disc_new_zone_radii.c

src/disc/disc_nsector.c

src/disc/disc_parameters.h

src/disc/disc_prototypes.h

src/disc/disc_show_thermal_zones.c

src/maths/generic_bisect.c

tbse