Subfield $f in datafield 245 can be preceded by $a. If this is the case, it should end in a comma.
Verified that for subfield 245, subfield a has a comma between it and subfield f.
<datafield ind1="1" ind2="0" tag="245">
<subfield code="a">REO Motor Car Company records,</subfield>
Tested and commas now appear in the MARC export between 245 tag subfield a and subfield f