Program: 81876
Project: 81876
Buggy source:
@SideOnly(Side.CLIENT) public EntityRotFX spawnFogParticle(double x,double y,double z,int parRenderOrder,TextureAtlasSprite tex){
  double speed=0D;
  Random rand=new Random();
  EntityRotFX entityfx=particleBehaviorFog.spawnNewParticleIconFX(Minecraft.getMinecraft().world,tex,x,y,z,(rand.nextDouble() - rand.nextDouble()) * speed,0.0D,(rand.nextDouble() - rand.nextDouble()) * speed,parRenderOrder);
  particleBehaviorFog.initParticle(entityfx);
  entityfx.setCanCollide(false);
  entityfx.callUpdatePB=false;
  boolean debug=false;
  if (debug) {
  }
 else {
  }
  if (levelCurIntensityStage == STATE_NORMAL) {
    entityfx.setMaxAge(300 + rand.nextInt(100));
  }
 else {
    entityfx.setMaxAge((size / 2) + rand.nextInt(100));
  }
  if (entityfx.getEntityId() % 20 < 5 && isSpinning()) {
    entityfx.renderOrder=1;
    entityfx.setMaxAge((size) + rand.nextInt(100));
  }
  float randFloat=(rand.nextFloat() * 0.6F);
  float baseBright=0.7F;
  if (levelCurIntensityStage > STATE_NORMAL) {
    baseBright=0.2F;
  }
 else   if (attrib_precipitation) {
    baseBright=0.2F;
  }
 else   if (manager.isVanillaRainActiveOnServer) {
    baseBright=0.2F;
  }
 else {
    float adj=Math.min(1F,levelWater / levelWaterStartRaining) * 0.6F;
    baseBright-=adj;
  }
  float finalBright=Math.min(1F,baseBright + randFloat);
  entityfx.setRBGColorF(finalBright,finalBright,finalBright);
  if (debug) {
    if (levelTemperature < 0) {
      entityfx.setRBGColorF(0,0,finalBright);
    }
 else     if (levelTemperature > 0) {
      entityfx.setRBGColorF(finalBright,0,0);
    }
  }
  return entityfx;
}

Fixed version (ground truth):
@SideOnly(Side.CLIENT) public EntityRotFX spawnFogParticle(double x,double y,double z,int parRenderOrder,TextureAtlasSprite tex){
  double speed=0D;
  Random rand=new Random();
  EntityRotFX entityfx=particleBehaviorFog.spawnNewParticleIconFX(Minecraft.getMinecraft().world,tex,x,y,z,(rand.nextDouble() - rand.nextDouble()) * speed,0.0D,(rand.nextDouble() - rand.nextDouble()) * speed,parRenderOrder);
  particleBehaviorFog.initParticle(entityfx);
  entityfx.setCanCollide(false);
  entityfx.callUpdatePB=false;
  boolean debug=false;
  if (debug) {
  }
 else {
  }
  if (levelCurIntensityStage == STATE_NORMAL) {
    entityfx.setMaxAge(300 + rand.nextInt(100));
  }
 else {
    entityfx.setMaxAge((size / 2) + rand.nextInt(100));
  }
  if (entityfx.getEntityId() % 20 < 5 && isSpinning()) {
    entityfx.renderOrder=1;
    entityfx.setMaxAge((size) + rand.nextInt(100));
  }
  float randFloat=(rand.nextFloat() * 0.6F);
  float baseBright=0.7F;
  if (levelCurIntensityStage > STATE_NORMAL) {
    baseBright=0.2F;
  }
 else   if (attrib_precipitation) {
    baseBright=0.2F;
  }
 else   if (manager.isVanillaRainActiveOnServer) {
    baseBright=0.2F;
  }
 else {
    float adj=Math.min(1F,levelWater / levelWaterStartRaining) * 0.6F;
    baseBright-=adj;
  }
  float finalBright=Math.min(1F,baseBright + randFloat);
  entityfx.setRBGColorF(finalBright,finalBright,finalBright);
  if (debug) {
    if (levelTemperature < 0) {
      entityfx.setRBGColorF(0,0,finalBright);
    }
 else     if (levelTemperature > 0) {
      entityfx.setRBGColorF(finalBright,0,0);
    }
  }
  ExtendedRenderer.rotEffRenderer.addEffect(entityfx);
  particleBehaviorFog.particles.add(entityfx);
  return entityfx;
}