tests/bug_0057.phpt failed once in CI on ffi linux-x86_64 (passed on re-run) #257

On Dependabot PR #247 (run 37012905963, job ffi - linux-x86_64) tests/bug_0057.phpt failed with refiner: upstream error in the DiskANN queryVector test. A re-run of the failed job passed with no code change, so the test or the DiskANN refiner is nondeterministic. Worth finding the cause (data race, timing, or index build state).