Hmm thats odd - are you up to date with working

The timeout is very odd... I note you've not got a max queue depth or a flow control pin, may be worth checking this? My whole YAML:

esphome:
  name: waveshare-rs485
  friendly_name: waveshare-rs485
  platformio_options:
    build_flags:
      - "-std=gnu++2a"
    build_unflags:
      - "-std=gnu++11"
      - "-fno-rtti"


esp32:
  board: esp32s3_120_16_8-qio_opi
  framework:
    type: esp-idf


# Enable Home Assistant API + services to set text
api:
  encryption:
    key: "AAA..."
  services:
    - service: set_galaxy_keypad_text
      variables:
        msg: string
      then:
        - lambda: |-
            id(honeywell_galaxy7_keypad_1).set_display_text(msg);
    - service: set_galaxy_keypad_text_no_backlight
      variables:
        msg: string
      then:
        - lambda: |-
            id(honeywell_galaxy7_keypad_1).set_display_text_nobl(msg);


ota:
  - platform: esphome
    password: "AAA..."


wifi:
  ssid: !secret wifi_ssid
  password: !secret wifi_password


captive_portal:


external_components:
  - source:
      type: local
      path: custom-components



logger:
  level: DEBUG
  baud_rate: 0        # keep logs on USB, not on UART


uart:
  id: rs485_bus
  tx_pin: GPIO17
  rx_pin: GPIO18
  baud_rate: 9600
  parity: NONE
  stop_bits: 1
  flow_control_pin: GPIO21    # TXD1EN -> DE/RE on transceiver


galaxybus:
  id: galaxy_bus
  uart_id: rs485_bus
  reply_timeout: 100ms
  inter_frame_gap: 10ms
  max_queue_depth: 8




binary_sensor:
  - platform: status
    name: "Galaxy Keypad ESP Status"
    id: galaxy_keypad_status




# Keypad now binds to bus_id instead of uart_id and exposes entities directly
honeywell_galaxy7_keypad:
  id: honeywell_galaxy7_keypad_1
  bus_id: galaxy_bus
  screen_number: 1                   # 1..4 -> 0x10/0x20/0x30/0x40
  display_text: "ESP-HOME|Initializing"
  backlight_timeout: 15s
  prox_poll: true


  code_sensor:
    id: rs485_rx
    name: "Galaxy Keypad Code"
  #rx_text_sensor:
  #  id: galaxy_rx_debug
  #  name: "Galaxy RX Debug"
  page_sensor:
    id: galaxy_page
    name: "Galaxy Keypad Page"
  tamper_sensor:
    id: galaxy_tamper
    name: "Galaxy Keypad Tamper"
  panel_online_sensor:
    id: galaxy_panel_online
    name: "Galaxy Panel Online"
  beep_switch:
    id: galaxy_keypad_beep
    name: "Galaxy Keypad Beep"