[mpl]

Not sure it can helps here. But just wondered of {data} table content, when you have selected track with loaded rs5k instance on the note 60 (exactly as in your project).

So,
1) In action list select Script: mpl_RS5k manager (background).lua, open in IDE with Reascript>Edit.
2) In line 35 change

local data = {}

to

data = {}

3) hit Cmd+S
4) open project you attached and select a track with loaded sample
5) make screenshot of variables window.

Here is what I see when loading your project: