It looks like an issue with how the new data is loaded. Check that home_team and away_time have both integer dtype. You can make sure they are integers with home_team.astype(int)
Also, side note, the rugby example was updated recently but the docs have not been updated with that yet. You may want to also take a look at https://nbviewer.jupyter.org/github/pymc-devs/pymc-examples/blob/main/examples/case_studies/rugby_analytics.ipynb