Program: 169625
Project: 169625
Buggy source:
@Override public void update(){
  super.update();
  if (ticks % 60 == 0) {
    HashMap<ForgeDirection,TileEntity> oldConnections=connections;
    connections=new HashMap();
    boolean sender=false;
    boolean receiver=false;
    for (    ForgeDirection dir : ForgeDirection.VALID_DIRECTIONS) {
      TileEntity tile=toPos().add(dir).getTileEntity(world());
      if (tile != null) {
        connections.put(dir,tile);
        if (tile instanceof IRadioWaveSender) {
          sender=true;
        }
        if (tile instanceof IRadioWaveReceiver) {
          receiver=true;
        }
      }
    }
    if (sender && receiver) {
      if (grid == null) {
        grid=WirelessGridManager.getOrCreateGrid(world(),this,gridName,gridKey);
        for (        TileEntity tile : connections.values()) {
          if (tile instanceof IRadioWaveReceiver) {
            grid.connect((IRadioWaveReceiver)tile);
          }
          if (tile instanceof IRadioWaveSender) {
            grid.connect((IRadioWaveSender)tile);
          }
        }
        grid.connect(this,null);
      }
 else {
        for (        TileEntity tile : oldConnections.values()) {
          if (!connections.values().contains(tile)) {
            if (tile instanceof IRadioWaveReceiver) {
              grid.disconnect((IRadioWaveReceiver)tile);
            }
            if (tile instanceof IRadioWaveSender) {
              grid.disconnect((IRadioWaveSender)tile);
            }
          }
        }
        for (        TileEntity tile : connections.values()) {
          if (!oldConnections.values().contains(tile)) {
            if (tile instanceof IRadioWaveReceiver) {
              grid.connect((IRadioWaveReceiver)tile);
            }
            if (tile instanceof IRadioWaveSender) {
              grid.connect((IRadioWaveSender)tile);
            }
          }
        }
        if (!grid.overlaps(new Pos(this))) {
          grid.disconnect(this);
        }
      }
    }
 else     if (grid != null) {
      grid.disconnect(this);
      grid=null;
    }
  }
}

Fixed version (ground truth):
@Override public void update(){
  super.update();
  if (isServer() && ticks % 60 == 0) {
    HashMap<ForgeDirection,TileEntity> oldConnections=connections;
    connections=new HashMap();
    boolean sender=false;
    boolean receiver=false;
    for (    ForgeDirection dir : ForgeDirection.VALID_DIRECTIONS) {
      TileEntity tile=toPos().add(dir).getTileEntity(world());
      if (tile != null) {
        connections.put(dir,tile);
        if (tile instanceof IRadioWaveSender) {
          sender=true;
        }
        if (tile instanceof IRadioWaveReceiver) {
          receiver=true;
        }
      }
    }
    if (sender && receiver) {
      if (grid == null) {
        grid=WirelessGridManager.getOrCreateGrid(world(),this,gridName,gridKey);
        for (        TileEntity tile : connections.values()) {
          if (tile instanceof IRadioWaveReceiver) {
            grid.connect((IRadioWaveReceiver)tile);
          }
          if (tile instanceof IRadioWaveSender) {
            grid.connect((IRadioWaveSender)tile);
          }
        }
        grid.connect(this,null);
      }
 else {
        for (        TileEntity tile : oldConnections.values()) {
          if (!connections.values().contains(tile)) {
            if (tile instanceof IRadioWaveReceiver) {
              grid.disconnect((IRadioWaveReceiver)tile);
            }
            if (tile instanceof IRadioWaveSender) {
              grid.disconnect((IRadioWaveSender)tile);
            }
          }
        }
        for (        TileEntity tile : connections.values()) {
          if (!oldConnections.values().contains(tile)) {
            if (tile instanceof IRadioWaveReceiver) {
              grid.connect((IRadioWaveReceiver)tile);
            }
            if (tile instanceof IRadioWaveSender) {
              grid.connect((IRadioWaveSender)tile);
            }
          }
        }
        if (!grid.overlaps(new Pos(this))) {
          grid.disconnect(this);
        }
      }
    }
 else     if (grid != null) {
      grid.disconnect(this);
      grid=null;
    }
  }
}