Hey,
same here…I have another post and thought it would be related to the python node which is doing weard stuff…but I figured its really the rdkit molecules.
System: Ubuntu 16.04 LTS
KNIME: 3.7.1
RDKit KNIME integration 3.6.0.v201903281548
Python: Anaconda environment with python 3.6.7 and rdkit 2019.03.1.0 (error was also there for the latest 2018 release, just upgraded today) pyarrow 0.11.0
It was also reported here: Forum post
In the meantime I thought it was solved but might be due to my update on 3.7.1 (was using 3.6.1 before)