Firebase Analytics prevent City from being tracked

We are using FirebaseAnalytics in our Android app. By default, demographic info (such as country, city) is extracted/derived from the ip adress. How can we disable this from being tracked? Country would be ok-ish, but the City absolutely needs to be absent/null! We work with medical records, and it's absolutely critical that no one is able to get city level details about demographics. Ideally, the field is just not present in the BigQuery Schema!

We tried 2 things:

1) Update Big Query Schema

Delete the geo.city column from Big Query. Unfortunately, Big Query creates a new export every day. So we would need to know where those fields are coming from. Something we don't know.

2) DefaultParameters within the app

Tried to use default parameters from inside the app, so the city will always be null.

        Bundle defaultValues = new Bundle();
        defaultValues.putString("geo.city", null);
        FirebaseAnalytics.getInstance(ctx).setDefaultEventParameters(defaultValues);

Unfortunately, we still see geo.city in our BigQuery data filled in.

Anyone has suggestions?

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