For removing the tags, the macro uses the Select Menu Item > Tag > Remove Tags, pauses, then calls the script for tagging with @done and @due(time).
When it’s in this mood, though, the jumping down a line will happen even when I “manually” select the menu item or use the Taskpaper designated shortcut for removing tags. I noticed it because of my KM macro, but it doesn’t happen exclusively with my macro.
This will happen when you “clear tags” and the text cursor is near the end of the items text … basically it’s maintaining text offset position (from start of document), but since the tag text is removed … that offset position end up in the next entry. This is something that I eventually need to fix. Until then you can work around the problem by first moving the text cursor to the very start of the entries text … then the problem should never happen.