have you ever noticed whether the actual auditioned RT is immediately above or below the one you selected ? If so, it could be an array subscript problem. (zero based or one based)

Another possibility is that if you SORTED the list of real tracks, and auditioned the 5th item in the sorted list, it might audition the 5th item in the list BEFORE it was sorted. You could test that theory by counting down the list next time you get the wrong instrument to see which array subscript you clicked, then unsort the list and cound down again the same number of subscripts and audition that RT... if it's the same one then RB is displaying RTs by the sorted list, but auditioning them to the unsorted list.

Or not. I'm just kickin' ideas around.

But these are common programming problems with sorted arrays... usually both arrays are still in memory, and it's easy to update one reference to the array (used to display the array's contents) but not the other (used to process an item picked from the array).

https://www.dropbox.com/sh/ey71h8ep047758h/AAC12jNM0Hz9Q8zsh5iDeqNHa?dl=0