Fender Poti 500

I've bought several of these and I'm disappointed.

First of all the rating is all over the place. They are supposed to have a 10% tolerance. So they could be anywhere from 450k to 550k. But among the ones I've received there are some within this range but also ones as low as 410k and as high as 609k.

Second. The last order contained three of them. Two work, and the third first had loud crackles when turning, and lates ceased working. Now when I turn it is does nothing.