OK first thing is head spacing...It looks like you are setting the shoulder back too much. The case is going inside the chamber too deeply and when held by the extractor hook the case is stretching out when fired. The way to correct that is to back off on the sizing die, you will want the case to fit the barrel and be within 0.0"(Flush to the barrel hood) to -0.002" below as a max.
What is happening is every time you fire them, it is working the brass at the shoulder and usually the separation occurs at the shoulder or neck, however it can separate anywhere on the case as it tries to stretch back out, to fill the chamber dimensions.
I size mine to be as flush with the barrel hood as possible. The less case expansion front to back the better!
Good luck and best regards!
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