Fire and Forget
New brass is maleable, which means it can be 'worked' or sized, or sometimes made to flow, like fire forming in a rifle chamber.
Each time the brass is fired, tremendous pressure generated by the powder makes the brass harder slightly, or somewhat brittle.
Hot loads make brass brittle faster, while lighter load can take longer to make the brass brittle. Its hard to predicate how long this takes.
When brass gets brittle it can create weak spots, especially where it is worked the most, like the case mouth. A weakness usually manifests itself as a split, albeit very small. You probably missed it when you reloaded it, or it was there all along, it just wasn't prominent enough.
Hot loads like the 5.0 of 231 in a weaker case with a small split will behave exactly as the pictured ones.
This is why suspect cases, cases with prominent bulges [especially around the base] and cases with small visible spits at the case mouth should never be reloaded.