Program: 27626
Project: 27626
Buggy source:
@Override public boolean setLocationAndRotation(Location location,Vector3f rotation,EnumSet<RelativePositions> relativePositions){
  if (relativePositions.isEmpty()) {
    if (setLocation(location)) {
      setRotation(rotation);
      return true;
    }
    return false;
  }
 else {
    if (((Entity)this) instanceof EntityPlayerMP) {
      EnumSet<S08PacketPlayerPosLook.EnumFlags> relativeFlags=EnumSet.noneOf(S08PacketPlayerPosLook.EnumFlags.class);
      if (relativePositions.contains(RelativePositions.X)) {
        relativeFlags.add(S08PacketPlayerPosLook.EnumFlags.X);
      }
      if (relativePositions.contains(RelativePositions.Y)) {
        relativeFlags.add(S08PacketPlayerPosLook.EnumFlags.Y);
      }
      if (relativePositions.contains(RelativePositions.Z)) {
        relativeFlags.add(S08PacketPlayerPosLook.EnumFlags.Z);
      }
      if (relativePositions.contains(RelativePositions.PITCH)) {
        relativeFlags.add(S08PacketPlayerPosLook.EnumFlags.Y_ROT);
      }
      if (relativePositions.contains(RelativePositions.YAW)) {
        relativeFlags.add(S08PacketPlayerPosLook.EnumFlags.X_ROT);
      }
      ((EntityPlayerMP)(Entity)this).playerNetServerHandler.func_175089_a(location.getPosition().getX(),location.getPosition().getY(),location.getPosition().getZ(),rotation.getX(),rotation.getY(),relativeFlags);
      return true;
    }
 else {
      Location resultant=getLocation();
      Vector3f resultantRotation=getRotation();
      if (relativePositions.contains(RelativePositions.X)) {
        resultant.add(location.getPosition().getX(),0,0);
      }
      if (relativePositions.contains(RelativePositions.Y)) {
        resultant.add(0,location.getPosition().getY(),0);
      }
      if (relativePositions.contains(RelativePositions.Z)) {
        resultant.add(0,0,location.getPosition().getZ());
      }
      if (relativePositions.contains(RelativePositions.PITCH)) {
        resultantRotation.add(rotation.getX(),0,0);
      }
      if (relativePositions.contains(RelativePositions.YAW)) {
        resultantRotation.add(0,rotation.getY(),0);
      }
      if (setLocation(resultant)) {
        setRotation(resultantRotation);
        return true;
      }
      return false;
    }
  }
}

Fixed version (ground truth):
@SuppressWarnings({"String_Node_Str","String_Node_Str"}) @Override public boolean setLocationAndRotation(Location location,Vector3f rotation,EnumSet<RelativePositions> relativePositions){
  if (relativePositions.isEmpty()) {
    if (setLocation(location)) {
      setRotation(rotation);
      return true;
    }
    return false;
  }
 else {
    if (((Entity)this) instanceof EntityPlayerMP) {
      EnumSet relativeFlags=EnumSet.noneOf(EnumFlags.class);
      if (relativePositions.contains(RelativePositions.X)) {
        relativeFlags.add(EnumFlags.X);
      }
      if (relativePositions.contains(RelativePositions.Y)) {
        relativeFlags.add(EnumFlags.Y);
      }
      if (relativePositions.contains(RelativePositions.Z)) {
        relativeFlags.add(EnumFlags.Z);
      }
      if (relativePositions.contains(RelativePositions.PITCH)) {
        relativeFlags.add(EnumFlags.Y_ROT);
      }
      if (relativePositions.contains(RelativePositions.YAW)) {
        relativeFlags.add(EnumFlags.X_ROT);
      }
      ((EntityPlayerMP)(Entity)this).playerNetServerHandler.func_175089_a(location.getPosition().getX(),location.getPosition().getY(),location.getPosition().getZ(),rotation.getX(),rotation.getY(),relativeFlags);
      return true;
    }
 else {
      Location resultant=getLocation();
      Vector3f resultantRotation=getRotation();
      if (relativePositions.contains(RelativePositions.X)) {
        resultant.add(location.getPosition().getX(),0,0);
      }
      if (relativePositions.contains(RelativePositions.Y)) {
        resultant.add(0,location.getPosition().getY(),0);
      }
      if (relativePositions.contains(RelativePositions.Z)) {
        resultant.add(0,0,location.getPosition().getZ());
      }
      if (relativePositions.contains(RelativePositions.PITCH)) {
        resultantRotation.add(rotation.getX(),0,0);
      }
      if (relativePositions.contains(RelativePositions.YAW)) {
        resultantRotation.add(0,rotation.getY(),0);
      }
      if (setLocation(resultant)) {
        setRotation(resultantRotation);
        return true;
      }
      return false;
    }
  }
}