Yay for visualisation!
This map was really opaque until yEd helped explain the problem...
Very cool. It's interesting to see that all the loops are all crisscrosses until the last few before *Z. I guess that's how they ensured Z stayed at the end of the loop (by requiring RRRR and only having RRRR at the end of the instructions).
Nice, you can clearly see each input is going to loop