Six rejections in a row and then I changed exactly one line on my resume

Summary line at the top used to be a generic "detail-oriented software engineer with X years of experience." Swapped it for one sentence naming the actual kind of problem I want to work on and a real number from my last role. Nothing else changed — same bullets, same formatting. Next four applications got three screens. Small sample size, could be coincidence, but it's the only variable that moved.