BF-41512is caused by a test correctness issue in migration_fails_with_spurious_documents.js‎. The migration is succeeding when it is expected to fail. This check's logic is wrong because it possible that if we have Chunk A and Chunk B on the targetShard, that Chunk B is the chunk that would conflict with the spurious document but we could return Chunk A early which would then succeed. The logic for how chunks is returned has been modified on master, which is why this issue only exists on v8.0-staging.