1. Is this with all garrisons or only those of a certain type? Is this behavior present with vanilla units as well in your mod?
2. It would probably be in the squad_ui_ext but I'm not sure. Other possibilities would be squad_type, entity type, and entity UI. I don't know what the specific setting is to get an announcement. You can easily compare instances by ctrl+clicking them on the left tree.
1. it doesnt happen with vanilla units.
2. i checked squad type and its the same. I dont see an entity type and ui type.
I tested making a new squad of the unit without changing anything and it has a spawn voice and voice. I noticed that the game gave it a grenadier voice even though its an obersoldaten group. I was using wehrmacht.