Richard
I have the same set up as you almost. I have 3 KY29s camera with D40 backs.I have a BRD80 and BRD85 and they work flawlessly.Do you have sync going to your decks. Most of the time when you get the servo light to flicker and stay on you have lost sync. Can you hook you camera to a monitor and see if the tape is playing ok in the D40 just to eliminate that as a problem
One other thing I have found that I had more trouble out of the 124min tapes then anything. I stop buying them years ago. I only use 104s or 64s way to many dropouts and sync problems. Maybe it was just me but the color did not seem as crisp due to thinner tape,just my opinion