Some of the tracks in my library show the wrong length when I add that column, or when exporting to CSV.
They are mostly encoded with LAME 3.97, according to EncSpot; but I have plenty of 3.97 encoded files which don't show this error. It's what I usually use to rip CDs, in conjunction with Exact Audio Copy. Those that are wrong all seem to be shown as eight times their true length, although I haven't checked them all.
There is also one album which was encoded with LAME 3.92, and on that the tracks are shown as four times their true length.
EncSpot reports the correct lengths for all the above.
Is this a problem with my encoding set-up (which doesn't change all that often); a bug in MP3tag; or incompetence on my part somewhere else?