How to Trap Error Executing B75C003 WritetoFlatFile function?

We have a custom UBE running on the iSeries OS400 which uses function B75C003 WritetoFlatFile to write records. Most of the records are writing successfully, but some are being dropped. We haven't found any discernible pattern as to which records get dropped. The debug log shows the error 022U is occurring, but that is a generic error that it failed to write the line. Looking at the code for the function, it happens when it compares a count of the characters it tried to write to a count of the characters actually written.

Is there anything we can do on the iSeries side to get to a more informative error message?