Some of the mold cups on certain molds are a little more worn than others. These mold cups are several decades old and wear down over time. With this, some chips will come out thicker than others due to inconsistencies in pressing due to wear. This is more noticeable on some molds in comparison to others. CSQ and DSQ seem to have the most problems with this.
My B-mold set has some uneven barrels but not to the degree of my CSQ Rounders and DSQ sets. The only time is really bothers me is if a barrel is too thick to fit in a rack, in which after that, it's mostly trial and error trying to pick out the thicker chips and exchange them with thinner ones to make all the barrels fit.