That is not my experience, so I would have to see it to believe it.
Works fine in the portable version here. Could have something to do with the path to mp3tag.exe or %_folderpath%. You know... Windows quirks with spaces in the path or maybe upper case letters? The standard installed version has already told Windows where it lives.
Yes indeed same exact portable version that had bug with jumping list worked fine for files located on another hard drive, so it must be something with the path or folder structure.
I believe i found what causes the problem with list scrolling down, if you have filter (F3) open then it scrolls upon using action to select, if not open then it does not scroll.