It is not possible to produce the exact same pants time and time again, as there's always a margin within the measurements. One pair of pants may be within measurements, at the top of the range while another pair may be within measurements, but at the bottom of the range, therefore the difference between these two pairs becomes noticeable.
Our pants are made so that they take the shape of the individual wearing them, we usually say that the more you wear them, the better they become. The feeling between a new pair and an older pair of pants can therefore be experienced very differently.
Different color baths and coating applications can make the material feel different even though the composition is the same, this can also affect the fit of the pants.
When we work with an ongoing collection, we make updates along the way to improve our products every time, we may therefore have updated the fit or adjusted a measurement in-between two seasons.