How to correct format the dimension of the validation set - time series

I'm trying to understand how to add my validation data into my LSTM. At the moment I'm loading the train and the test set in the following way:

1. First of all I load my time series from a directory, where they have a 2D shape (#values, #n_features = 30):

   self.train = np.load(os.path.join(data, train, X0train_s30.npy))
   self.test = np.load(os.path.join(data, test, X0test_s30.npy))
   # Shape for LSTM
   self.shape_data(self.train)
   self.shape_data(self.test, train=False)
   

2. Then I proceeded with shaping it for preparing the input for the LSTM. Since they are time series, I decided a number of steps:

   def shape_data(self, arr, train=True):
      Shape raw input streams for ingestion into LSTM. config.l_s specifies
      the sequence length of prior timesteps fed into the model at
      each timestep t.
   
      Args:
          arr (np array): array of input streams with
              dimensions [timesteps, 1, input dimensions]
          train (bool): If shaping training data, this indicates
              data can be shuffled
      
      data = []
      for i in range(len(arr) - self.config.l_s - self.config.n_predictions):
          data.append(arr[i:i + self.config.l_s + self.config.n_predictions])
      data = np.array(data)
   
   
      assert len(data.shape) == 3
   
      if train:
          np.random.shuffle(data)
          self.X_train = data[:, :-self.config.n_predictions, :]
          self.y_train = data[:, -self.config.n_predictions:, 0]  # telemetry value is at position 0
      else:
          self.X_test = data[:, :-self.config.n_predictions, :]
          self.y_test = data[:, -self.config.n_predictions:, 0]  # telemetry value is at position 0
   

On this way the final train shape is (51324, 250, 30) and the final test shape is (51324, 10). This is the model built, which works perfectly:

cbs = [History(), EarlyStopping(monitor='val_loss',
                                    patience=self.config.patience,
                                    min_delta=self.config.min_delta,
                                    verbose=0)]

self.model = Sequential()

self.model.add(LSTM(
    self.config.layers[0],
    input_shape=(None, channel.X_train.shape[2]),
    return_sequences=True))
self.model.add(Dropout(self.config.dropout))

self.model.add(LSTM(
    self.config.layers[1],
    return_sequences=False))
self.model.add(Dropout(self.config.dropout))

self.model.add(Dense(
    self.config.n_predictions))
self.model.add(Activation('linear'))

self.model.compile(loss=self.config.loss_metric,
                   optimizer=self.config.optimizer)

self.model.fit(channel.X_train,
               channel.y_train,
               batch_size=self.config.lstm_batch_size,
               epochs=self.config.epochs,
               validation_split=self.config.validation_split,
               callbacks=cbs,
               verbose=True)

Now, I decided to add a validation .npy array, which I loaded and shaped on the same format of the train set (is this correct?):

def shape_val(self, arr, train=True):
    data = []
    for i in range(len(arr) - self.config.l_s - self.config.n_predictions):
        data.append(arr[i:i + self.config.l_s + self.config.n_predictions])
    data = np.array(data)
    assert len(data.shape) == 3
    np.random.shuffle(data)
    self.X_val = data[:, :-self.config.n_predictions, :]

Then, I changed the fit function of my model on the following way:

self.model.fit(channel.X_train,
               channel.y_train,
               batch_size=self.config.lstm_batch_size,
               epochs=self.config.epochs,
               validation_data=(channel.X_val, channel.X_val),
               callbacks=cbs,
               verbose=True)

If I try to run it I get the error:

File /opt/anaconda3/envs/telemanom/lib/python3.6/site-packages/keras/engine/training.py, line 1175, in fit batch_size=batch_size)

File /opt/anaconda3/envs/telemanom/lib/python3.6/site-packages/keras/engine/training.py, line 621, in _standardize_user_data exception_prefix='target')

File /opt/anaconda3/envs/telemanom/lib/python3.6/site-packages/keras/engine/training_utils.py, line 135, in standardize_input_data 'with shape ' + str(data_shape))

ValueError: Error when checking target: expected activation_1 to have 2 dimensions, but got array with shape (13769, 250, 30)

Am I formatting the validation set correctly? Or am I missing something important?