Thanks @Peng_Lu for discovering an error in the forecast_evaluation module of the AI_WQ_package.
Full details of the issue can be found in the thread titled Question about RPSS Evaluation.
It get the latest calculation of the RPSS, please update the python package using:
python3 -m pip install --upgrade AI_WQ_package
It should update to v2.2.
Thanks all, and sorry for the inconvenience.
Josh