Administrators may notice that the 'Default' checkbox under Case Assignment Checkbox in a Case page layout's Layout Properties is unchecked after deploying the page layout from a source organization to a target organization using a Change Set or the Metadata API (ANT migration tool).
This behavior is observed even if the 'Default' checkbox was checked in the source organization before deployment.
This is expected behavior. The 'Default' checkbox state is not preserved in deployment unless the Show on Edit Page checkbox is also enabled in the source organization's page layout settings before deployment.
The 'Default' checkbox behavior is controlled by two Metadata API page layout properties:
showRunAssignmentRulesCheckbox is also enabled.In simple terms: the 'Show on Edit Page' checkbox must be checked in the source org before deployment — otherwise, the 'Default' value does not carry over to the target org.
Special Behavior in Deployments
Components Available in Change Sets
Layouts - Metadata API Developer Guide
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