The bug:

The overlay of trimmed armor phases in and out of the base texture on the side of the item when moving on the screen while held in the hand.

Steps to reproduce:

• Obtain trimmed armor that has parts of the trim overlay texture extending to the side of the base texture and hold in your hand (first person or third).
• Slowly move your head while paying attention to the side the item.
• Notice the pixels from the trim overlay flicker while phasing in and out of the base texture it lays over

Examples of affected items:

• /give @s netherite_helmet{Trim:
  Unknown macro: {material}

  }

• /give @s netherite_leggings{Trim:
  Unknown macro: {material}

  }

• /give @s netherite_boots{Trim: {material: "minecraft:gold" ,pattern: "minecraft:sentry"}

  }