Mlflow's Postgresql chart PVC isn't deleted when enabled is set to false. This means if you enable this plugin, then disable it, then re-enable it, the old PVC will be used when redeployed and the credentials will be wrong. This shows up as an error in the mlflow tracking pod which says something to the effect that postgres user bn_mlflow can't log in due to credentials.
A workaround is to disable mlflow, delete the PVC manually, then re-enable it.