That's correct, the fill occurs correctly, but the fault still occurs. I have since resolved the problem - the fault was not related to the fill. At another point in the code, I was unintentionally modifying some of the items in the fill, and the system was attempting to write the changes back to the database. Ultimately the fault led to discovering an error in my code, but I still do not understand why it was being raised. Although it's a stub, there is an implemented sync method with the prescribed signature.
OK. I don't have the code available at the moment, but when I get back to it, I'll post the syncItems method from the assembler and the Action Script code that was raising the fault. The data service configuration is posted verbatim above.