In ArcGIS Pro 3.1.5, I am using Model Builder to iterate feature classes from a source GDB database containing data. The iterated features are then appended to a target empty GDB database with identical field structures. I configured the field matching type to 'Reconcile field differences using field mapping' to align corresponding fields. However, during model execution, the field mapping only applies the schema from the first iterated feature class, failing to dynamically adjust field mappings for subsequent feature classes. This results in mismatches for datasets with differing field orders or missing fields.
I wonder if modelbuilder has the same requirements on how to use fieldmapping as does its implementation notes for python
Append (Data Management)—ArcGIS Pro | Documentation
note the bullet points regarding when fieldmapping needs to occur
If the target feature class does indeed have 'identical field structures', couldn't you just use the 'Input fields must match target fields' field matching type? If so, it shouldn't matter if field mapping is lost during iteration as it isn't' used.
R_