Error "-123" when training

Hello,
I’m having an error, when initializing training. On the website it just says “-123” in an alert box.
The logs say
starting training process
C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\site-packages\sklearn\cross_validation.py:44: DeprecationWarning: This module was deprecated in version 0.18 in favor of the model_selection module into which all the refactored classes and functions are moved. Also note that the interface of the new CV iterators are different from that of this module. This module will be removed in 0.20.
“This module will be removed in 0.20.”, DeprecationWarning)
Using MXNet backend.
C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\site-packages\mxnet\module\bucketing_module.py:385: UserWarning: Optimizer created manually outside Module but rescale_grad is not normalized to 1.0/batch_size/num_workers (1.0 vs. 0.0078125). Is this intended?
force_init=force_init)
C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\site-packages\keras\engine\training.py:1575: UserWarning: Epoch comprised more than samples_per_epoch samples, which might affect learning results. Set samples_per_epoch correctly to avoid this warning.
warnings.warn('Epoch comprised more than ’
Traceback (most recent call last):
File “backend\data_gen.py”, line 59, in data_gen.threadsafe_iter.next
File “backend\data_gen.py”, line 387, in DataGenerator
File “backend\data_gen.py”, line 128, in data_gen.get_batch_data
File “C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\site-packages\pandas\core\series.py”, line 601, in getitem
result = self.index.get_value(self, key)
File “C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\site-packages\pandas\core\indexes\base.py”, line 2477, in get_value
tz=getattr(series.dtype, ‘tz’, None))
File “pandas_libs\index.pyx”, line 98, in pandas._libs.index.IndexEngine.get_value (pandas_libs\index.c:4404)
File “pandas_libs\index.pyx”, line 106, in pandas._libs.index.IndexEngine.get_value (pandas_libs\index.c:4087)
File “pandas_libs\index.pyx”, line 154, in pandas._libs.index.IndexEngine.get_loc (pandas_libs\index.c:5126)
File “pandas_libs\hashtable_class_helper.pxi”, line 759, in pandas._libs.hashtable.Int64HashTable.get_item (pandas_libs\hashtable.c:14031)
File “pandas_libs\hashtable_class_helper.pxi”, line 765, in pandas._libs.hashtable.Int64HashTable.get_item (pandas_libs\hashtable.c:13975)
KeyError: -123
Traceback (most recent call last):
File “backend\data_gen.py”, line 59, in data_gen.threadsafe_iter.next
StopIteration
Traceback (most recent call last):
File “backend\data_gen.py”, line 59, in data_gen.threadsafe_iter.next
StopIteration
Exception in thread Thread-11:
Traceback (most recent call last):
File “C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\threading.py”, line 914, in _bootstrap_inner
self.run()
File “C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\threading.py”, line 862, in run
self._target(*self._args, **self._kwargs)
File “C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\site-packages\keras\engine\training.py”, line 433, in data_generator_task
generator_output = next(self._generator)
File “backend\data_gen.py”, line 57, in data_gen.threadsafe_iter.next
File “backend\data_gen.py”, line 65, in data_gen.threadsafe_iter.next
File “backend\data_gen.py”, line 59, in data_gen.threadsafe_iter.next
StopIteration

Traceback (most recent call last):
File “backend\data_gen.py”, line 59, in data_gen.threadsafe_iter.next
StopIteration
Exception in thread Thread-9:
Traceback (most recent call last):
File “C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\threading.py”, line 914, in _bootstrap_inner
self.run()
File “C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\threading.py”, line 862, in run
self._target(*self._args, **self._kwargs)
File “C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\site-packages\keras\engine\training.py”, line 433, in data_generator_task
generator_output = next(self._generator)
File “backend\data_gen.py”, line 57, in data_gen.threadsafe_iter.next
File “backend\data_gen.py”, line 65, in data_gen.threadsafe_iter.next
File “backend\data_gen.py”, line 59, in data_gen.threadsafe_iter.next
File “backend\data_gen.py”, line 387, in DataGenerator
File “backend\data_gen.py”, line 128, in data_gen.get_batch_data
File “C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\site-packages\pandas\core\series.py”, line 601, in getitem
result = self.index.get_value(self, key)
File “C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\site-packages\pandas\core\indexes\base.py”, line 2477, in get_value
tz=getattr(series.dtype, ‘tz’, None))
File “pandas_libs\index.pyx”, line 98, in pandas._libs.index.IndexEngine.get_value (pandas_libs\index.c:4404)
File “pandas_libs\index.pyx”, line 106, in pandas._libs.index.IndexEngine.get_value (pandas_libs\index.c:4087)
File “pandas_libs\index.pyx”, line 154, in pandas._libs.index.IndexEngine.get_loc (pandas_libs\index.c:5126)
File “pandas_libs\hashtable_class_helper.pxi”, line 759, in pandas._libs.hashtable.Int64HashTable.get_item (pandas_libs\hashtable.c:14031)
File “pandas_libs\hashtable_class_helper.pxi”, line 765, in pandas._libs.hashtable.Int64HashTable.get_item (pandas_libs\hashtable.c:13975)
KeyError: -123

Exception in thread Thread-10:
Traceback (most recent call last):
File “C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\threading.py”, line 914, in _bootstrap_inner
self.run()
File “C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\threading.py”, line 862, in run
self._target(*self._args, **self._kwargs)
File “C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\site-packages\keras\engine\training.py”, line 433, in data_generator_task
generator_output = next(self._generator)
File “backend\data_gen.py”, line 57, in data_gen.threadsafe_iter.next
File “backend\data_gen.py”, line 65, in data_gen.threadsafe_iter.next
File “backend\data_gen.py”, line 59, in data_gen.threadsafe_iter.next
StopIteration

Exception in thread Thread-12:
Traceback (most recent call last):
File “C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\threading.py”, line 914, in _bootstrap_inner
self.run()
File “C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\threading.py”, line 862, in run
self._target(*self._args, **self._kwargs)
File “C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\site-packages\keras\engine\training.py”, line 433, in data_generator_task
generator_output = next(self._generator)
File “backend\data_gen.py”, line 57, in data_gen.threadsafe_iter.next
File “backend\data_gen.py”, line 65, in data_gen.threadsafe_iter.next
File “backend\data_gen.py”, line 59, in data_gen.threadsafe_iter.next
StopIteration

Traceback (most recent call last):
File “backend\data_gen.py”, line 59, in data_gen.threadsafe_iter.next
StopIteration
Exception in thread Thread-13:
Traceback (most recent call last):
File “C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\threading.py”, line 914, in _bootstrap_inner
self.run()
File “C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\threading.py”, line 862, in run
self._target(*self._args, **self._kwargs)
File “C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\site-packages\keras\engine\training.py”, line 433, in data_generator_task
generator_output = next(self._generator)
File “backend\data_gen.py”, line 57, in data_gen.threadsafe_iter.next
File “backend\data_gen.py”, line 65, in data_gen.threadsafe_iter.next
File “backend\data_gen.py”, line 59, in data_gen.threadsafe_iter.next
StopIteration

Traceback (most recent call last):
File “backend\data_gen.py”, line 59, in data_gen.threadsafe_iter.next
StopIteration
Exception in thread Thread-14:
Traceback (most recent call last):
File “C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\threading.py”, line 914, in _bootstrap_inner
self.run()
File “C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\threading.py”, line 862, in run
self._target(*self._args, **self._kwargs)
File “C:\Users\USERA\AppData\Local\Programs\DeepLearningStudio\conda3\lib\site-packages\keras\engine\training.py”, line 433, in data_generator_task
generator_output = next(self._generator)
File “backend\data_gen.py”, line 57, in data_gen.threadsafe_iter.next
File “backend\data_gen.py”, line 65, in data_gen.threadsafe_iter.next
File “backend\data_gen.py”, line 59, in data_gen.threadsafe_iter.next
StopIteration

Dataset is Image to Image, 16x16 Pixels, black and white.

Does anyone know, what this means? It doesn’t seem to a mistake, that I made.
Best