BUG: time series plot on HDFML

This error arrised. What is it's origin?

2020-11-18 10:45:33,454 - INFO: PlotTimeSeries finished after 0:00:01 (hh:mm:ss)  [time_tracking.py:__exit__:131]
2020-11-18 10:45:33,454 - ERROR: 'AxesSubplot' object does not support indexing  [run_environment.py:__exit__:137]
Traceback (most recent call last):
  File "/p/project/deepacf/intelliaq/leufen1/mlair/mlair/workflows/abstract_workflow.py", line 32, in run
    stage(**self._registry_kwargs[pos])
  File "/p/project/deepacf/intelliaq/leufen1/mlair/mlair/run_modules/post_processing.py", line 81, in __init__
    self._run()
  File "/p/project/deepacf/intelliaq/leufen1/mlair/mlair/run_modules/post_processing.py", line 104, in _run
    self.plot()
  File "/p/project/deepacf/intelliaq/leufen1/mlair/mlair/run_modules/post_processing.py", line 292, in plot
    sampling=self._sampling)
  File "/p/project/deepacf/intelliaq/leufen1/mlair/mlair/helpers/time_tracking.py", line 40, in __call__
    return self.__wrapped__(*args, **kwargs)
  File "/p/project/deepacf/intelliaq/leufen1/mlair/mlair/plotting/postprocessing_plotting.py", line 764, in __init__
    self._plot(plot_folder)
  File "/p/project/deepacf/intelliaq/leufen1/mlair/mlair/plotting/postprocessing_plotting.py", line 807, in _plot
    self._plot_obs(axes[pos], plot_data)
TypeError: 'AxesSubplot' object does not support indexing
2020-11-18 10:45:33,485 - INFO: DefaultWorkflowHPC finished after 0:23:20 (hh:mm:ss)  [run_environment.py:__del__:118]
2020-11-18 10:45:33,485 - DEBUG: get: logging_path(general)=None  [datastore.py:track:122]