Error miscalculation in GA model.

I have a genetic algorithm model. It records the optimized variables in every iteration and stores in an array. The array also contains the calculated error for every iteration. Most of the errors match their corresponding variable values, but there are always a few that do not. Why is that? How can I fix it? I have set rng to default for reproducibility. Thank you.

[Walter Roberson]

The values might not match if there is a constraint violation.