Program: 12693
Project: 12693
Buggy source:
private boolean placeTent(World worldIn,Random rand,BlockPos position,EnumFacing facing){
  IBlockState ground=worldIn.getBlockState(position.down());
  if (ground.getBlock().isSideSolid(ground,worldIn,position.down(),EnumFacing.UP)) {
    BlockPos tl=worldIn.getHeight(position.offset(facing).offset(facing.rotateYCCW()));
    BlockPos bl=worldIn.getHeight(position.offset(facing.rotateYCCW()));
    BlockPos tr=worldIn.getHeight(position.offset(facing));
    if (Math.abs(tl.getY() - position.getY()) < 2 && Math.abs(bl.getY() - position.getY()) < 2 && Math.abs(tr.getY() - position.getY()) < 2) {
      tl=new BlockPos(tl.getX(),position.getY(),tl.getZ());
      bl=new BlockPos(bl.getX(),position.getY(),bl.getZ());
      tr=new BlockPos(tr.getX(),position.getY(),tr.getZ());
      if (!checkGroundAndPos(worldIn,tl,ground))       return false;
      if (!checkGroundAndPos(worldIn,bl,ground))       return false;
      if (!checkGroundAndPos(worldIn,tr,ground))       return false;
      ItemTent.placeAt(worldIn,position,facing,true,true);
      BlockPos entrance1=position.offset(facing.getOpposite());
      BlockPos entrance2=position.offset(facing.getOpposite()).offset(facing.rotateYCCW());
      worldIn.setBlockToAir(entrance1);
      worldIn.setBlockToAir(entrance2);
      if (rand.nextInt(3) == 0) {
        this.setBlockAndNotifyAdequately(worldIn,worldIn.getHeight(entrance1.offset(facing.getOpposite())),Blocks.CRAFTING_TABLE.getDefaultState());
      }
      if (rand.nextInt(3) == 0) {
        this.setBlockAndNotifyAdequately(worldIn,worldIn.getHeight(entrance2.offset(facing.getOpposite())),Blocks.TORCH.getDefaultState());
      }
    }
    return true;
  }
  return false;
}

Fixed version (ground truth):
private boolean placeTent(World worldIn,Random rand,BlockPos position,EnumFacing facing){
  IBlockState ground=worldIn.getBlockState(position.down());
  if (ground.getBlock().isSideSolid(ground,worldIn,position.down(),EnumFacing.UP)) {
    BlockPos tl=worldIn.getHeight(position.offset(facing).offset(facing.rotateYCCW()));
    BlockPos bl=worldIn.getHeight(position.offset(facing.rotateYCCW()));
    BlockPos tr=worldIn.getHeight(position.offset(facing));
    if (Math.abs(tl.getY() - position.getY()) < 2 && Math.abs(bl.getY() - position.getY()) < 2 && Math.abs(tr.getY() - position.getY()) < 2) {
      tl=new BlockPos(tl.getX(),position.getY(),tl.getZ());
      bl=new BlockPos(bl.getX(),position.getY(),bl.getZ());
      tr=new BlockPos(tr.getX(),position.getY(),tr.getZ());
      if (!checkGroundAndPos(worldIn,tl,ground))       return false;
      if (!checkGroundAndPos(worldIn,bl,ground))       return false;
      if (!checkGroundAndPos(worldIn,tr,ground))       return false;
      ItemTent.placeAt(worldIn,position,facing,true,true);
      BlockPos entrance1=position.offset(facing.getOpposite());
      BlockPos entrance2=position.offset(facing.getOpposite()).offset(facing.rotateYCCW());
      worldIn.setBlockToAir(entrance1);
      worldIn.setBlockToAir(entrance2);
      if (rand.nextInt(3) == 0) {
        this.setBlockAndNotifyAdequately(worldIn,worldIn.getHeight(entrance1.offset(facing.getOpposite())),Blocks.CRAFTING_TABLE.getDefaultState());
      }
      if (rand.nextInt(3) == 0) {
        this.setBlockAndNotifyAdequately(worldIn,worldIn.getHeight(entrance2.offset(facing.getOpposite())),Blocks.TORCH.getDefaultState());
      }
      return true;
    }
  }
  return false;
}