Yeah, I discovered what those advance buttons are for after eventually getting to that part in the owner's manual. For about 2 weeks I had been using the "<<" and ">>" buttons on the Control screen to "scrub" through songs (which I thought was a pain because I first had to navigate to that screen before I could get access those buttons). So, it was a great discovery when I learned I could simply use the advance buttons under the control knob to fast forward, rewind, and navigate to previous and next tracks!(which, by the way, TX, DOES allow you to scrub through a song if you hold it down!)
By the way...seems silly to only post this in the A5 Q&A just because I have an A5. There are a lot of issues common to both A5 and S5.
I can't speak to your shuffle mode issue, as I never use the shuffle function.
As for common issues applicable to both A5 & S5, maybe that's something Andrew can consider for the site refresh he's working on (i.e., perhaps have a new section). I'll bring it to his attention.