Cannot add two equality constraints to nlopt - nlopt

Question

I am using nlopt in C, and I would like to add a set of vector equality constraint and a single equality constraint. Here is a sample of my code:
nlopt_opt opt;
opt = nlopt_create(NLOPT_GN_ISRES, (P.N));
nlopt_set_upper_bounds(opt, ub);
nlopt_set_lower_bounds(opt, lb);
nlopt_set_min_objective(opt, F, &P);
printf("\nAdding constraint_A: %d", nlopt_add_equality_mconstraint(opt, (P.N), constraint_A, &P, mtol_c));
printf("\nAdding constraint_B: %d", nlopt_add_equality_constraint(opt, constraint_B, &P, tol_c));
Constraints A and B are defined as follows:
void constraint_A(unsigned Q, double* result, unsigned N, const double *x, double *grad, void *data){
param *p = (param*)data;
unsigned int i, j;
if (grad) {
for(i=0; i<((*p).N); i++){
for(j=0; j<((*p).N); j++){
grad[((*p).N)*i+j] = ((*p).dx)*((*p).q)[((*p).N)*i+j] / ((*p).r)[i];
}
}
}
for(i=0; i<((*p).N); i++){
for(result[i]=0.0, j=0; j<((*p).N); j++){
result[i] += x[j]*((*p).q)[((*p).N)*i+j];
}
result[i] = ( ((*p).dx)*result[i]-((*p).r)[i] ) / ((*p).r)[i];
}
}
double constraint_B(unsigned N, const double *x, double *grad, void *data){
param *p = (param*)data;
double result;
unsigned int i;
if(grad){
for(i=0; i<((*p).N); i++){
grad[i] = ((*p).dx)*gsl_pow_2(((*p).x)[i]);
}
}
for(result=0.0, i=0; i<((*p).N); i++){
result += x[i]*gsl_pow_2(((*p).x)[i]);
}
result = ((*p).dx)*result-1.0;
return result;
}
where dx, q, r and x are elements of the data structure P.
I obtain the output
Adding constraint_A: 1
Adding constraint_B: -2
If I reverse the order of the operations as follows
printf("\nAdding constraint_B: %d", nlopt_add_equality_constraint(opt, constraint_B, &P, tol_c));
printf("\nAdding constraint_A: %d", nlopt_add_equality_mconstraint(opt, (P.N), constraint_A, &P, mtol_c));
I still obtain
Adding constraint_B: 1
Adding constraint_A: -2
Whenever the return code for one constraint is negative, the constraint is ignored in the optimization.
Why is the constraint return code negative? Are the two constraint inconsistent with each other?