My inputs and outputs are not lining up when using Integer decision variables

Essentially Platypus will say my best input is [False, True,False] which is 2 and gives the objective 5. But when I do objective(2) I get either infeasible or a different objective. Below is a minimal reproducible example. Which has a list of random values r and the following problem: (Please excuse the awful formatting and pseudo maths, Github doesn't seem to like maths)

$$ Min. r_{x1} * r{x_2} $$

$$ S.T. x_1 \ne x_2 $$

$$ x_1 \mod 2 ==1
$$

$$ x_2 \mod 2 ==1 $$

import platypus as plt
import numpy as np

n = 8
r = np.arange(n) +1

_res = []
def obj(x):
    x = [x[0], x[1]]
    result = r[x[0]] * r[x[1]]
    t_stat = (x[0]%2) * (x[1])%2 * (x[0]!=x[1])
    _res.append(dict(x= x, result=result, t_stat=t_stat))
    return [result], [int(t_stat)]

n_iter=100
_res = []

prob = plt.Problem(2,1, 1)
prob.types[:] = [plt.Integer(1,n-1),plt.Integer(1,n-1)]
prob.function = obj
prob.constraints[0] = plt.Constraint("==", 1.0)
algo = plt.NSGAII(prob)
algo.run(n_iter)

all_res = [r for r in algo.result]
valid_res = [r for r in algo.result if r.feasible]

Now compare the platypus valid_res with the ones we tracked ourselves in _res. Look at valid_res and chose an objective value, here I choose 16. Then consider which inputs gives the result 16 in _res, in my experience there is no overlap

>>> [r for r in _res if r["result"] == 16]
[{'x': [3, 3], 'result': 16, 't_stat': 0}, {'x': [7, 1], 'result': 16, 't_stat': 1}, {'x': [1, 7], 'result': 16, 't_stat': 1}, {'x': [7, 1], 'result': 16, 't_stat': 1}, {'x': [1, 7], 'result': 16, 't_stat': 1}]
>>> [r for r in valid_res if r.objectives[0] == 16]
[Solution[[True, False, True],[False, False, False]|16|0.0], Solution[[False, False, False],[True, False, True]|16|0.0], Solution[[True, False, True],[False, False, False]|16|0.0], Solution[[False, False, False],[True, False, True]|16|0.0]]

So here _res is saying [3,3] (not this isn't feasible) and [7,1] give the output. While valid_res gives [[True, False, True],[False, False, False]] which is equal to [5,0], but note that our Integer space starts at 1 (plt.Integer(1,n-1) so I think 0 represents 1, as such the platypus result is [6,1]

Note This isn't the actual problem I'm trying to solve, in my actual problem Platypus says the best objective is achieved with inputs [0,56] and my _res says [1,48] gets these results. I have also tried this with plt.Integer(0,n-1) and found the same issue.

So my question is, why are the platypus recorded inputs not aligning with their outputs?

Project-Platypus / Platypus

My inputs and outputs are not lining up when using Integer decision variables #200