Daddario PL009 Single String

I bought several single strings to have as a backup. Just before the show I decided to change all the strings and use the E string I had bought as a single string. I immediately noticed that the string did not hold the tuning and went out of tune easily. I thought the string needed more stretching which I did. At the soundcheck I noticed that the string absolutely did not hold the tuning, the winding that holds the final ball was loosening. I immediately took another of the single strings I had bought, same exact behavior: pulling the string to tune it, the more you pulled, the looser the winding that holds the final ball became. I had to go find a store near the venue to buy more strings.
So far I have never had any problems with Daddario strings, but after this experience I will probably switch to another brand.