Weird CRASH caused by use of _sym-type symbols in an external on Max 9

On Max 9.0.5 running on a MacBook M1 Air laptop, I just observed a very strange reproducible crash, which can be demonstrated in the minimal external code below.

Note that in the jw_bang method there are 4 illustrative cases which were tested individually and in each case where a _sym-type symbol was used instead of a gensym-type symbol it crashed. I will include the CMakeLists.txt file at the end as well.

#include "ext.h"
#include "ext_obex.h"
#include "commonsyms.h"

typedef struct _jw
{
    t_object ob;  // the object itself (must be first)
    void* outlet; // one outlet
} t_jw;

void* jw_new(void);
void jw_free(t_jw* x);
void jw_assist(t_jw* x, void* b, long m, long a, char* s);
void jw_bang(t_jw* x);

void* jw_class;

void ext_main(void* r)
{
    t_class* c;

    c = class_new("jw", (method)jw_new, (method)jw_free, (long)sizeof(t_jw),
                  0L /* leave NULL!! */, A_NOTHING, 0);

    class_addmethod(c, (method)jw_bang,   "bang",   0);

    class_register(CLASS_BOX, c);
    jw_class = c;
}

void jw_free(t_jw* x)
{
    ;
}

void* jw_new(void)
{
    t_jw* x = NULL;
    if ((x = (t_jw*)object_alloc(jw_class))) {
        x->outlet = outlet_new(x, NULL);
    }
    return (x);
}

void jw_bang(t_jw* x)
{
    // NO CRASH
    t_object* mytable = (t_object*)object_new(gensym("nobox"), gensym("table"));
    object_free(mytable);

    // CRASH
    t_object* mytable = (t_object*)object_new(_sym_nobox, _sym_table);
    object_free(mytable);

    // NO CRASH
    t_object* jsonwriter = (t_object*)object_new(gensym("nobox"), gensym("jsonwriter"));
    object_free(jsonwriter);

    // CRASH
    t_object* jsonwriter = (t_object*)object_new(_sym_nobox, _sym_jsonwriter);
    object_free(jsonwriter);

    outlet_bang(x->outlet);
}

Here is the CMakeLists.txt file used:

include(${CMAKE_CURRENT_SOURCE_DIR}/../../max-sdk-base/script/max-pretarget.cmake)

include_directories( 
	"${MAX_SDK_INCLUDES}"
	"${MAX_SDK_MSP_INCLUDES}"
	"${MAX_SDK_JIT_INCLUDES}"
)

file(GLOB PROJECT_SRC
     "*.h"
     "*.c"
     "*.cpp"
)
add_library( 
	${PROJECT_NAME} 
	MODULE
	${PROJECT_SRC}
	"${MAX_SDK_INCLUDES}/common/commonsyms.c"
)

include(${CMAKE_CURRENT_SOURCE_DIR}/../../max-sdk-base/script/max-posttarget.cmake)