Can you update the version and filter definition for review?
Its possible that some of the issue related to LCM is about a Bug which could have been fixed in a Patch !!
Can you share the error message and your EPM Versions.
we're using 22.214.171.124 the filter that imports ok looks something like this:
Where we get issues is where the filter I think contains multiple single members some of which may be enclosed in quotes ie:
"xxx_YY_zz" as the flat file then has a comma separated value with double quotes as it shows ,""xxx_YY_zz"",
Hope that sheds some light on the issue.