In shuffle everything(not sure which shuffle mode), I press tweek order and get the message "match found", but no change is displayed in the now & next display. In fact the next song has not changed.

In this particular example i tried tweek artist and tweek album, neither worked. I noted that the tweek by title didnt work, but I am not sure if this has ever worked. I see in Tony's button guide that this is lable "future functionality". So thats probably expected not to work.

Had you just performed an Insert? The tweaks will fall after the insert. (I think.)