onChange rule will not trigger when assigned under Foundation Object.
Example: onChange rule to set a custom field in 'Location' object when any of field in Location is changed.
Result: The custom fields are not set and Location page keeps on loading forever.
SAP SuccessFactors Employee Central - Foundation Objects
On Foundation Object UI only onInit and onSave rules are supported.
Kindly raise this as an Enhancement Request as per KBA 2090228 - How to Submit Enhancement Requests for SAP SuccessFactors Products
onChange rule in foundation object Manage Organization pay and job structures , KBA , LOD-SF-EC-FOO , Foundation Objects (Organisation, Pay and Job Structures) , LOD-SF-EC , Employee Central , LOD-SF-EC-RUL , DO NOT USE - Business Rules & Event Derivation , Product Enhancement