Program: 95770
Project: 95770
Buggy source:
public boolean checkForMultiBlock(){
  if (!this.worldObj.isRemote) {
    int xPos=this.findArrayXPosition();
    int yPos=this.findArrayYPosition();
    int zPos=this.findArrayZPosition();
    int xSize=this.findArrayXSize();
    int ySize=this.findArrayYSize();
    int zSize=this.findArrayZSize();
    for (int x=this.xCoord - xPos; x < this.xCoord - xPos + xSize; x++) {
      for (int y=this.yCoord - yPos; y < this.yCoord - yPos + ySize; y++) {
        for (int z=this.zCoord - zPos; z < this.zCoord - zPos + zSize; z++) {
          if (this.isSameTank(this.worldObj.getTileEntity(x,y,z))) {
            TileEntityTank tank=(TileEntityTank)this.worldObj.getTileEntity(x,y,z);
            int[] tankSize=tank.findArrayDimensions();
            if (!(xSize == tankSize[0] && ySize == tankSize[1] && zSize == tankSize[2])) {
              return false;
            }
          }
 else {
            return false;
          }
        }
      }
    }
    for (int x=this.xCoord - xPos; x < this.xCoord - xPos + xSize; x++) {
      for (int y=this.yCoord - yPos; y < this.yCoord - yPos + ySize; y++) {
        for (int z=this.zCoord - zPos; z < this.zCoord - zPos + zSize; z++) {
          TileEntityTank tank=((TileEntityTank)this.worldObj.getTileEntity(x,y,z));
          if (tank.isMultiBlock()) {
            tank.breakMultiBlock();
          }
        }
      }
    }
    int lvl=0;
    for (int x=this.xCoord - xPos; x < this.xCoord - xPos + xSize; x++) {
      for (int y=this.yCoord - yPos; y < this.yCoord - yPos + ySize; y++) {
        for (int z=this.zCoord - zPos; z < this.zCoord - zPos + zSize; z++) {
          TileEntityTank tank=((TileEntityTank)this.worldObj.getTileEntity(x,y,z));
          lvl=tank.fluidLevel + lvl;
        }
      }
    }
    this.connectedTanks=xSize * ySize * zSize;
    for (int x=this.xCoord - xPos; x < this.xCoord - xPos + xSize; x++) {
      for (int y=this.yCoord - yPos; y < this.yCoord - yPos + ySize; y++) {
        for (int z=this.zCoord - zPos; z < this.zCoord - zPos + zSize; z++) {
          TileEntityTank tank=((TileEntityTank)this.worldObj.getTileEntity(x,y,z));
          tank.connectedTanks=xSize * ySize * zSize;
          tank.setFluidLevel(lvl);
        }
      }
    }
    return true;
  }
  return false;
}

Fixed version (ground truth):
public boolean checkForMultiBlock(){
  if (!this.worldObj.isRemote) {
    int xPos=this.findArrayXPosition();
    int yPos=this.findArrayYPosition();
    int zPos=this.findArrayZPosition();
    int xSize=this.findArrayXSize();
    int ySize=this.findArrayYSize();
    int zSize=this.findArrayZSize();
    if (xSize == 1 && ySize == 1 && zSize == 1)     return false;
    for (int x=this.xCoord - xPos; x < this.xCoord - xPos + xSize; x++) {
      for (int y=this.yCoord - yPos; y < this.yCoord - yPos + ySize; y++) {
        for (int z=this.zCoord - zPos; z < this.zCoord - zPos + zSize; z++) {
          if (this.isSameTank(this.worldObj.getTileEntity(x,y,z))) {
            TileEntityTank tank=(TileEntityTank)this.worldObj.getTileEntity(x,y,z);
            int[] tankSize=tank.findArrayDimensions();
            if (!(xSize == tankSize[0] && ySize == tankSize[1] && zSize == tankSize[2])) {
              return false;
            }
          }
 else {
            return false;
          }
        }
      }
    }
    for (int x=this.xCoord - xPos; x < this.xCoord - xPos + xSize; x++) {
      for (int y=this.yCoord - yPos; y < this.yCoord - yPos + ySize; y++) {
        for (int z=this.zCoord - zPos; z < this.zCoord - zPos + zSize; z++) {
          TileEntityTank tank=((TileEntityTank)this.worldObj.getTileEntity(x,y,z));
          if (tank.isMultiBlock()) {
            tank.breakMultiBlock();
          }
        }
      }
    }
    int lvl=0;
    for (int x=this.xCoord - xPos; x < this.xCoord - xPos + xSize; x++) {
      for (int y=this.yCoord - yPos; y < this.yCoord - yPos + ySize; y++) {
        for (int z=this.zCoord - zPos; z < this.zCoord - zPos + zSize; z++) {
          TileEntityTank tank=((TileEntityTank)this.worldObj.getTileEntity(x,y,z));
          lvl=tank.fluidLevel + lvl;
        }
      }
    }
    this.connectedTanks=xSize * ySize * zSize;
    for (int x=this.xCoord - xPos; x < this.xCoord - xPos + xSize; x++) {
      for (int y=this.yCoord - yPos; y < this.yCoord - yPos + ySize; y++) {
        for (int z=this.zCoord - zPos; z < this.zCoord - zPos + zSize; z++) {
          TileEntityTank tank=((TileEntityTank)this.worldObj.getTileEntity(x,y,z));
          tank.connectedTanks=xSize * ySize * zSize;
          tank.setFluidLevel(lvl);
          tank.markDirtyAndMarkForUpdate();
        }
      }
    }
    return true;
  }
  return false;
}