Addressable RGB Light (WS2815) flickers when using ESP32-S3

I want to drive an addressable RGB light strip (12V, WS2815) via an ESP32-S3 running ESPHome.

I have the following setup but the issue that the light flickers:

I also have an ESP32 (WT32-ETH01) with WLED attached this way and the light is rock solid:

Any ideas what the issue is? The .yaml code for the ESPHome:

# PC Desk Controller
substitutions:
comment: "Modular ESP32 Controller (LED, Switches & More)"
device_name: base-desk-controller
friendly_name: (BASE) Desk Controller

esphome:
name: ${device_name}
friendly_name: ${friendly_name}
comment: ${comment}

esp32:
board: esp32-s3-devkitc-1
framework:
type: arduino

# Enable logging
logger:

# T-ETH-ELite
ethernet:
type: W5500
clk_pin: GPIO48
mosi_pin: GPIO21
miso_pin: GPIO47
cs_pin: GPIO45
interrupt_pin: GPIO14
#reset_pin: GPIOXX

light:
- platform: neopixelbus
type: GRB
variant: WS2812
pin: 4
num_leds: 34
name: "NeoPixel Light"

# Light also flickers with this:
# - platform: fastled_clockless
# chipset: WS2812
# pin: 4
# num_leds: 34
# rgb_order: GRB
# name: "FastLED WS28xx Light"