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One set of headers for replicate fields will always be sent in the CAS/Liaison API files, even if there is no data in those fields. [Typically these are the xxx.xxxx.xx0 field names].
The source format is only looking at the header rows in the most recent 15 files since the last remap date
Field mappings are persistent, so dummy files that contain all of the headers for relevant fields can be deleted once they are mapped