Well, you say that, but I'm perfectly capable of understanding that electrical components exhibit low levels of noise on signal lines. Having reread your posts, what I get from it is: "Those two channels, B1/D1, are subject to more noise than the others, due to board layout and so on, and it looks like the modules don't have much tolerance for that." Correct?
I did do some googling to see if you were right, and I'm seeing a number of posts with people having similar issues, where playing with the voltages/timings did absolutely nothing. Interesting.