I'm curious to hear what you think is the culprit. I remember speaking with support a year or so ago when I got my indexer before erasing my setup by accidentally loading a different custom configuration and they told me the indexer motorwas not programmed at the factory. Or something to that effect.
This morning I turned on the indexer with the 140.0000 value I had been using. Typing a 360 command output about 180 degrees of rotation real world. So no idea why it magically changed but I doubled it so my b unit value was around 280.0000. I then proceeded to trial and error using a square and a couple notches on the top of the indexer motor bracket and Chuck. I started with mb 360 and made adjustments to the value until it was as close as I could detect. I then did a mb 3600, and then MB 5400, and every time fine tuning going back and forth between mb 0 and MB multiples of 360. This is obviously not the most scientific way but after 60 rotations or so, the marks are as close as I can tell dead on. Unit value isn't in front of me but it was somewhere in the 277.7500 range.
PRS Alpha 96" X 48" w/ 12" Z
4hp Spindle
6" Indexer
Aspire 8