About 7 or 8 years ago, when they were still in Somerset, Simpsons had a run of shedders. A lot of guys on the shaving forums were complaining about them and got replacements. The company was very small in terms of workforce at that time, and the problem was traced to a relatively inexperienced lady who had taken over the knot installation while the regular employee was out sick. They got it straightened out.

There was also a run of brushes that had split, or bent, ends on the bristles. I don't have personal experience with that, but DrP, the renowned Simpson collector, told me about it. The bristles, he said, were very nearly abrasive. Beyond scritchy. Point being, stuff happens. Adding to what thebigspendur said, it isn't as if the makers have a consistent supply of badger bristle that is exactly the same from batch to batch.

As in the tobacco pipe world, material is batch graded. IOW, what might be a Super or a Finest badger in one batch, could be a Best or a Heritage in another. Rooney (Lee Sabini) hasn't been able to get the Finest bristle in years. If he could I'm thinking he would.