Text file-to-Tag w. %_filename% as Safety Tag

I frequently use %_filename% as the first field in a Text file to Tag conversion, to make sure the entries in the text file align with the target mp3's. This feature only seems to work with a single folder (i.e., fails when I have targets in multiple folders in the text file).
Is this a flaw or am I misusing the feature?

note: I can copy-paste the %_filename% from a multi-destination text file into Windows File Explorer and it finds / plays the target mp3's fine ... it just won't update the tags. It's not a spelling error.

Scenario ... I download many (dozen) subscriptions from UCSD.edu which are in .mp4 format and I need to convert these to .mp3 for my ancient IPOD ... my converter (ffmpeg batch av converter) does not align all the tags correctly (and I do some customization).

Export script (partial) ...
UTF-8)$loop(%_filename%)%_filename%.mp3|%album%|^~|%track%|^~|
Import text string (partial) ...
%_filename_ext%|%album%|^~|%track%|^~

It works the current working directory.
If you want to address files in several folders you have to %_path% instead of %_filename% (and, of course, the corresponding data with a full path)

Thanks. I'm unavailable for a few days, so I'll test this on Monday and report back.

Thanks. That worked.
Given my scenario I needed to use:
%_folderpath%%_filename%.mp3