Hey,
First, iadded the image. Schematic is clearer now 
(or more clear?)
So the look back seems to work fine for item 4. I see nothing on item 5.
On the picture i supply with an extarnal power supply. I also did the same test supplying 4 and 5 via the arduino and the arduino with a 9V battery. It is excty the same.
(black big board is not plugged, excpet the power supply of the codeur)
I tried the first chain (first picture) with an external power supply, and nohting new. Neither item 4 or 5 ight up..