My 8th string keeps breaking! tips?

So my 8th keeps breaking at the locking-nut-thing because the locking-screw that holds the string in place. keeps getting in between the wounding of the string.

Because of the my string slowly gets pulled apart every time I either bend it at bit or chug hard on it.

I've been through 5 pair of strings now and only one of the pairs didn't have the problem.

I'm always very careful with how hard I lock the locking-thing but it seems to happen everytime.

I do use Strandberg strings.

Do any of you have any tips to how I can fixed it.