[Python] PANDAS pd.read_hdf works with some, but not all tables in my HDF5 file

I am using Pandas in Python 3.7 in order to read data from a HDF5 file. The HDF5 file contains tables of results from MSC Nastran.

The HDF5 file is named 'ave_01.h5'

The HDF5 table of displacements looks like this:



Using the following works just fine:

import numpy as np
import pandas as pd
pd.read_hdf('./ave_01.h5', 'NASTRAN/RESULT/NODAL/DISPLACEMENT')


However, I have another table for stress results, which looks like this:



So I would expect the following code to work, but it does not:

pd.read_hdf('./ave_01.h5', '/NASTRAN/RESULT/ELEMENTAL/STRESS/QUAD_CN')


I receive the following error:

ValueError: Wrong number of items passed 5, placement implies 1
​

I have noticed that this second table contains lists in some columns, whereas the first table does not. These lists also contain 5 elements. Perhaps this is causing the error, but I don't know if this is true, nor how to correct for this.

Where am I going wrong?

Thanks.

For reference, these results are of a simple test model, as can be seen below:

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