Ordering of loki entries with same timestamp is wrong

docker-compose.yml

version: "3"

services:
  loki:
    image: grafana/loki:2.6.1
    command: -config.file=/etc/loki/loki-config.yml
    ports:
      - "3100:3100"
    volumes:
      - ./loki-config.yml:/etc/loki/loki-config.yml
    logging:
      driver: json-file

  promtail:
    image: grafana/promtail:2.6.1
    command: -config.file=/etc/promtail/promtail-config.yml
    volumes:
      - ./promtail-config.yml:/etc/promtail/promtail-config.yml
      - ./logfile.log:/tmp/logfile.log
    depends_on:
      - loki
    logging:
      driver: json-file

  grafana:
    image: grafana/grafana:9.1.6
    environment:
      GF_LOG_LEVEL: error
    ports:
      - "3000:3000"
    volumes:
      - ./grafana-datasources.yml:/etc/grafana/provisioning/datasources/datasources.yml
    depends_on:
      - loki
    logging:
      driver: json-file

grafana-datasources.yml

---
datasources:
  - name: loki
    type: loki
    orgId: 1
    url: "http://loki:3100"

logfile.log

1664088800 OLDEST
1664088801 OLDER
1664088802 OLD
1664088803 THIS SHOULD BE RIGHT NEXT TO line 1
1664088804 line 01
1664088804 line 02
1664088804 line 03
1664088804 line 04
1664088804 line 05
1664088804 line 06
1664088804 line 07
1664088804 line 08
1664088804 line 09
1664088804 line 10
1664088804 line 11
1664088804 line 12
1664088804 line 13
1664088804 line 14
1664088804 line 15
1664088804 line 16
1664088804 line 17
1664088804 line 18
1664088804 line 19
1664088804 line 20
1664088805 THIS SHOULD BE RIGHT NEXT TO line 20
1664088806 NEW
1664088807 NEWER
1664088808 NEWEST
1664518226 NOW

loki-config.yml

auth_enabled: false

server:
  http_listen_port: 3100
  grpc_listen_port: 9096
  log_level: info

common:
  path_prefix: /tmp/loki
  storage:
    filesystem:
      chunks_directory: /tmp/loki/chunks
      rules_directory: /tmp/loki/rules
  replication_factor: 1
  ring:
    instance_addr: 127.0.0.1
    kvstore:
      store: inmemory

schema_config:
  configs:
    - from: 2020-10-24
      store: boltdb-shipper
      object_store: filesystem
      schema: v11
      index:
        prefix: index_
        period: 24h

limits_config:
  reject_old_samples: false
  reject_old_samples_max_age: 9600h
  max_query_length: 9600h # 400 days

ruler:
  alertmanager_url: http://localhost:9093

analytics:
  reporting_enabled: false

promtail-config.yml

server:
  http_listen_port: 9080
  grpc_listen_port: 0
  log_level: "debug"

positions:
  filename: /tmp/positions.yaml

clients:
  - url: http://loki:3100/loki/api/v1/push

scrape_configs:

- job_name: promtail
  pipeline_stages:
    - regex:
        expression: '^(?P<timestamp>\d+).*$'
    - timestamp:
        source: timestamp
        format: Unix
  static_configs:
    - targets:
        - localhost
      labels:
        job: sametimestamps
        __path__: /tmp/logfile.log