Consider the following Territory Hierarchy, these child territories - Commonly referred to as Country or Market Level Territories - do not have a common Parent Territory - Commonly referred to as the CORP Territory. A Customer System Admin user runs a mass assignment from the Territory Utilities tab on one of the top-level territory nodes:
The Mass Assignment processes all Zip-to-terr and Brick-to-terr records regardless of the Territory.
This is the expected behavior in this Territory setup. When multiple top-level Territory nodes exist in the Org and the Territory Mass Assignment is launched on one of these top-level nodes, the assignment process includes every Territory in the Mass Assignment process.
Create a single, top-level Territory - Usually referred to as a CORP territory - assign it as a parent territory of these Market or Country level territories.
CRM Help Documentation:
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