currently, it looks like that d:swarm is not able to process a file following OAI-PMH + mets/mods schema. It looks like that the schema determination by example doesn't work as expected for this schema*.
One possible solution might be to provide this schema as inbuilt schema as well, i.e., it will be derived by the containing XML schemata**.
*) at the end very complex schema by a rather comprehensive example (~41k statemens per record)
**) whereby, the concrete example contain custom namespace, e.g., 'slub'