WS2805 RGBCCT flickering at specific brightness/color combinations on ESP32 / WLED 0.16.0.1

[jlt24]

What happened?

I'm using 168 WS2805 RGB+CCT pixels with a QuinLED Dig-Quad running WLED 0.16.0.1.
I occasionally noticed very brief flashes from white LEDs that should not be illuminated. I was able to narrow this down to particular combinations of master brightness and color/CCT state.
The issue is especially reproducible with master brightness values 126–130 / 255. At brightness 128, a saved preset can reliably reproduce the flickering.
Known flickering state:

{
  "bri":128,
  "seg":[{
    "id":0,
    "bri":255,
    "cct":127,
    "col":[
      [255,206,166,0],
      [8,255,0,0],
      [0,0,0,0]
    ],
    "fx":0
  }]
}

Making a very small adjustment to the Kelvin/temperature slider stops the visible flickering without changing master brightness.
Stable state after that adjustment:

{
  "bri":128,
  "seg":[{
    "id":0,
    "bri":255,
    "cct":127,
    "col":[
      [255,214,177,0],
      [8,255,0,0],
      [0,0,0,0]
    ],
    "fx":0
  }]
}

Reloading the original saved preset causes the flickering to return.

Additional observations:

• Brightness 126–130 produces the issue most noticeably.
• Values immediately outside that range appeared stable during short tests.
• A very small Kelvin/temperature adjustment can eliminate the flicker.
• Sometimes the expected bad state doesn't immediately flicker, but changing to blue and then back to white causes it to return.
• The visible flashes appear to come from white emitters that should otherwise be off.
• This occurs directly from the WLED web interface, independent of Home Assistant/MQTT.
• Solid effect (fx:0) reproduces it.
• 168 WS2805 RGB+CCT pixels.
• GPIO 16.
• The problem appears related to the combination of brightness and color/CCT rather than brightness alone.
  Possibly related to Flickering - WS2805 - ESP32 C3 mini #5198, although that report is using ESP32-C3 while this setup uses a Dig-Quad/ESP32.

To Reproduce Bug

Hardware:

• QuinLED Dig-Quad / ESP32
• 168 WS2805 RGB+CCT pixels
• WLED 0.16.0.1
• WS2805 RGBCCT configured as the LED type
• Data GPIO 16

I can reproduce the flickering using the following steps:

1. Set the effect to Solid.
2. Set the master brightness to 128/255.
3. Set the LEDs to a warm white color.
4. With the following state, some of the white emitters that should not be illuminated will intermittently flash:

{
  "bri": 128,
  "seg": [{
    "id": 0,
    "bri": 255,
    "cct": 127,
    "col": [
      [255, 206, 166, 0],
      [8, 255, 0, 0],
      [0, 0, 0, 0]
    ],
    "fx": 0
  }]
}

Expected Behavior

No flicker

Install Method

Binary from WLED.me

What version of WLED?

0.16.0.1

Which microcontroller/board are you seeing the problem on?

ESP32

Relevant log/trace output

Anything else?

No response

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