Import-Export tag association

When I perform an export tag/import tag cycle on two tracks the tag associations are
swapped between tracks. If I redo the cycle a second time the tags are properly written to correct tracks. What is current mechanism of associating tag text with selected tracks in mp3tag database? Is there a method of ensuring or forcing an association? If I have an exported tag database containing tags of 10,000 tracks created previously, how can I reliably import this data into my current track database (which may contain new tracks and may not contain all tracks in the exported file database)?

If you export filename or path you can assign the tag row to the right file.
E.g. Export string:
%_path% | %artist% | %title%
Import string:
%_path% | %artist% | %title%