core: ERROR: "Client unable to keep up with pending messages. Stayed over 512 for 5 seconds" at the system log

The problem

ERROR: “Client unable to keep up with pending messages. Stayed over 512 for 5 seconds” appears at the system log constantly

Environment

subject	info
arch	armv7
chassis
dev	false
docker	true
docker_version	19.03.12
hassio	true
host_os	Raspbian GNU/Linux 10 (buster)
installation_type	Home Assistant Supervised
os_name	Linux
os_version	5.4.51-v7+
python_version	3.8.5
supervisor	245
timezone	Europe/Kiev
version	0.115.2
virtualenv	false

• Home Assistant Core release with the issue: 0.115.2
• Last working Home Assistant Core release (if known): don’t know
• Operating environment (OS/Container/Supervised/Core): Raspbian GNU/Linux 10 (buster)
• Integration causing this issue: don’t know
• Link to integration documentation on our website: don’t know

Problem-relevant configuration.yaml

homeassistant:
  name: "aaa"
  latitude: !secret latitude_coord
  longitude: !secret longitude_coord
  elevation: 179
  unit_system: metric
  time_zone: Europe/Kiev
  customize: !include includes/customize.yaml
  external_url: !secret external_url
  internal_url: !secret internal_url
  packages: !include_dir_merge_named includes/packages
  whitelist_external_dirs: 
    - /config  

config:

logger:
  default: info

frontend:
  themes: !include_dir_merge_named themes
  
map:  

mobile_app:

sun:

system_health:


updater:


http:
  ssl_certificate: /ssl/fullchain.pem
  ssl_key: /ssl/privkey.pem
  

lovelace:
  mode: yaml
  resources: !include includes/resources.yaml


history:


hacs:
  token: !secret HACS_github
  appdaemon: true
  python_script: true
  theme: true
  
google_assistant:
  project_id: !secret google_assistant_project_id
  exposed_domains:
   - switch
   - light
   - climate
   - mediaplayer
   - input_boolean
   - scene
   - script
   - sensor
   

tts:
  - platform: google_translate
  

mqtt:
  broker: core-mosquitto
  discovery: true
  discovery_prefix: homeassistant  
  username: !secret mqtt_username
  password: !secret mqtt_password
  
smartir:

timer: !include includes/timer.yaml
input_boolean: !include includes/input_boolean.yaml
input_number: !include includes/input_number.yaml
input_select: !include includes/input_select.yaml
group: !include includes/groups.yaml
scene: !include includes/scenes.yaml
recorder: !include includes/recorder.yaml
climate: !include includes/climate.yaml
zone: !include includes/zone.yaml
person: !include includes/person.yaml
telegram_bot: !include includes/telegram_bot.yaml
notify: !include includes/notify.yaml
remote: !include includes/remote.yaml

sensor: !include_dir_merge_list includes/sensor
automation: !include_dir_merge_list includes/automation
binary_sensor: !include_dir_merge_list includes/bin_sensor
script: !include_dir_merge_named includes/scripts
switch: !include_dir_merge_list includes/switches

Traceback/Error logs

Logger: homeassistant.components.websocket_api.http.connection.1844975792
Source: components/websocket_api/http.py:138
Integration: Home Assistant WebSocket API (documentation, issues)
First occurred: 00:37:19 (1 occurrences)
Last logged: 00:37:19
Client unable to keep up with pending messages. Stayed over 512 for 5 seconds 

Additional information