The exact details of how the Tweak Order function works are here, see if anything in there explains the behavior you were getting.

Things that come to mind immediately are:

- You're not shuffling the whole contents of the player, rather you are playing a short sub-playlist and therefore the artist in question does not exist more than once in your current list of songs.

- The other songs by that artist have already played and are "in the past" so it doesn't find them.

- You're holding down the button instead of pressing it, so it's filtering that artist out.

- The files weren't tagged properly so the artist is misspelled and therefore it's not finding a match.