It is possible to set different values for the localPref attribute on BGP advertisements with common pools, nodes, peers and aggregations lengths. This causes speakers to have more than one configuration of localPref for the same prefix. It is not guaranteed that speakers will use the same value.

https://github.com/metallb/metallb/issues/1739

Always

1. Create 2 BGP advertisements with the same pool, nodes, aggregation lengths and different localPref.
2. Delete one of the BGP ADV.
3. Recreate the previous BGP ADV.
4. Create a service.

Speakers will send BGP updates with different local preference.

All speakers must send BGP updates with the same local preference.