If you look at the output returned that is returned in the console, it looks like it is actually outputting the numbers as string values, (I suspect this as they are surrounded in quotes).
As a quick test I just created a basic playlist with 4 tracks, and added a code piece to the flow. In the code piece, you can see I created a simple array with the numbers 1 and 4 as the values inside of it, and then just returned them as the output. This does make the "message": "Invalid range_start parameter" error go away, but you will note it now returns undefined in its place, which may lead you believe it is still broken.
However, if you look at the gif I have provided below, you will see it does now indeed order the songs as expected.
Note: If the gif image is too small, simply right click it and click open image in new tab to view it full size.
I hope this helps.
Kind regards,
GunnerJnr