Here's a thing i did to investigate my multi-pass problem. The challenge is that with many passes each individual pass becomes less visible as it is averaged into the whole.
I made a tiny white dot and shined a VERY bright light on it so that the average value of the white pixels + all the background color passes remained high enough to be seen.
With that, I tested all the possible number of passes as it traversed a path and composited the renders together here.
Most of them are correctly subdivided, but a few, like 125, 144 and 169 fall short of where they should have gotten to on the path. Others, like 196 and 256, overshoot their goal and end up with multiple passes stacked on top of each other at the very end.
Eventually this will be part of an AMreport.