When using a large hosted feature layer as the input data in the Intersect and Apportion Polygon tools in ArcGIS Pro 3.2, it returns the error "999999".
ArcGIS Pro 3.4 includes improved error handling and messaging for issues that are caused by feature service/server instability. The error "999999" is replaced by an error code in series 003976-004006 that is returned by the server.