Love you (K)not

Urg. What is going on here? I spent years before I ever had the problem of knots in my skeins. At first I am sure this is because I was buying acrylic whatever yarns, but since then I have bought and knit a heck of a lot of yarn without much issue. In fact I couldn't really understand the hubbub everyone made about the knots in skeins.

Recently however I seem to have been seeing an unusally large number of knots. Let's keep track here of the "problem children" of just this year:

Caribbean Clown Socks - 2 knots in a total of 3 balls
China Doll Sweater - 1 knot in 2 balls
Quidditch Sweater - 3 knots in 6 balls
Bellatrix Socks - 1 knot in 1 ball

And I have started a bulky sweater with some more N.Y. Yarns Action only to find 1 knot and 1 horribly mangled area in the 2 skeins that I have used so far. Aaaaaaaah!

I have no idea why this is. It can't be a recent increase in the rate of knottiness in yarn production. I haven't bought yarn recently. This is all stash. And these are not yarns that particularly infamous for the number of knots. They aren't from the same yarn manufacturer or distributer. These aren't from wildly different from other yarns that I have used in the past. So what gives?