Program: 60004
Project: 60004
Buggy source:
@Override public boolean generate(World world,Random rand,int x,int y,int z){
  final int veinSize=genVeinSize;
  final int branchSize=1 + (veinSize / 30);
  final int subBranchSize=1 + (branchSize / 5);
  boolean r=false;
  for (int blocksVein=0; blocksVein <= veinSize; ) {
    int posX=x;
    int posY=y;
    int posZ=z;
    int directionChange=rand.nextInt(6);
    int directionX=rand.nextInt(2);
    int directionY=rand.nextInt(2);
    int directionZ=rand.nextInt(2);
{
      directionX+=~directionX >>> 31;
      directionX+=~directionY >>> 31;
      directionX+=~directionZ >>> 31;
    }
    for (int blocksBranch=0; blocksBranch <= branchSize; ) {
      if (directionChange != 1) {
        posX+=rand.nextInt(2) * directionX;
      }
      if (directionChange != 2) {
        posY+=rand.nextInt(2) * directionY;
      }
      if (directionChange != 3) {
        posZ+=rand.nextInt(2) * directionZ;
      }
      if (rand.nextInt(3) == 0) {
        int posX2=posX;
        int posY2=posY;
        int posZ2=posZ;
        int directionChange2=rand.nextInt(6);
        int directionX2=-rand.nextInt(2);
        int directionY2=-rand.nextInt(2);
        int directionZ2=-rand.nextInt(2);
{
          directionX2+=~directionX2 >>> 31;
          directionX2+=~directionY2 >>> 31;
          directionX2+=~directionZ2 >>> 31;
        }
        for (int blocksSubBranch=0; blocksSubBranch <= subBranchSize; ) {
          if (directionChange2 != 0) {
            posX2+=rand.nextInt(2) * directionX2;
          }
          if (directionChange2 != 1) {
            posY2+=rand.nextInt(2) * directionY2;
          }
          if (directionChange2 != 2) {
            posZ2+=rand.nextInt(2) * directionZ2;
          }
          r|=generateBlock(world,posX2,posY2,posZ2,genBlock,cluster);
          if (sparse) {
            blocksVein++;
            blocksBranch++;
          }
          blocksSubBranch++;
        }
      }
      r|=generateBlock(world,posX,posY,posZ,genBlock,cluster);
      blocksBranch++;
    }
    x=x + (rand.nextInt(3) - 1);
    y=y + (rand.nextInt(3) - 1);
    z=z + (rand.nextInt(3) - 1);
    blocksVein++;
  }
  return r;
}

Fixed version (ground truth):
@Override public boolean generate(World world,Random rand,int x,int y,int z){
  final int veinSize=genVeinSize;
  final int branchSize=1 + (veinSize / 30);
  final int subBranchSize=1 + (branchSize / 5);
  boolean r=false;
  for (int blocksVein=0; blocksVein <= veinSize; ) {
    int posX=x;
    int posY=y;
    int posZ=z;
    int directionChange=rand.nextInt(6);
    int directionX=-rand.nextInt(2);
    int directionY=-rand.nextInt(2);
    int directionZ=-rand.nextInt(2);
{
      directionX+=~directionX >>> 31;
      directionX+=~directionY >>> 31;
      directionX+=~directionZ >>> 31;
    }
    for (int blocksBranch=0; blocksBranch <= branchSize; ) {
      if (directionChange != 1) {
        posX+=rand.nextInt(2) * directionX;
      }
      if (directionChange != 2) {
        posY+=rand.nextInt(2) * directionY;
      }
      if (directionChange != 3) {
        posZ+=rand.nextInt(2) * directionZ;
      }
      if (rand.nextInt(3) == 0) {
        int posX2=posX;
        int posY2=posY;
        int posZ2=posZ;
        int directionChange2=rand.nextInt(6);
        int directionX2=-rand.nextInt(2);
        int directionY2=-rand.nextInt(2);
        int directionZ2=-rand.nextInt(2);
{
          directionX2+=~directionX2 >>> 31;
          directionX2+=~directionY2 >>> 31;
          directionX2+=~directionZ2 >>> 31;
        }
        for (int blocksSubBranch=0; blocksSubBranch <= subBranchSize; ) {
          if (directionChange2 != 0) {
            posX2+=rand.nextInt(2) * directionX2;
          }
          if (directionChange2 != 1) {
            posY2+=rand.nextInt(2) * directionY2;
          }
          if (directionChange2 != 2) {
            posZ2+=rand.nextInt(2) * directionZ2;
          }
          r|=generateBlock(world,posX2,posY2,posZ2,genBlock,cluster);
          if (sparse) {
            blocksVein++;
            blocksBranch++;
          }
          blocksSubBranch++;
        }
      }
      r|=generateBlock(world,posX,posY,posZ,genBlock,cluster);
      blocksBranch++;
    }
    x=x + (rand.nextInt(3) - 1);
    y=y + (rand.nextInt(3) - 1);
    z=z + (rand.nextInt(3) - 1);
    blocksVein++;
  }
  return r;
}