As
noted here by kjeron, basically the APPEND lines in fl#add_kit_ee#add_row should wrap the kitname in the UNLESS clauses with [ %TAB%]s, e.g. this
APPEND "%file%.2da" "%append%" UNLESS "%kit_name%"
becomes
APPEND "%file%.2da" "%append%" UNLESS "^[ %TAB%]*%kit_name%[ %TAB%]+"
A modder was using kits named foo and foobar and the latter would fail to append as needed.