The one most important missing bit is the sensor ring, these allways get overlooked despite having the hardest time, covered in rust shit crap etc, make sure each ring has clearly defined segments, as that is what the sensor needs to see, apart from that as above, note I do not think your problem is a ring but would check these anyway, it is most likely as said a connection somewhere, you can be certain it will be the last one you look at though!!
Good luck.
tabetha