OlfCNC, I am not faulting UCCNC, it works just fine. I am working with a Teknic engineer to find the problem, not UCCNC.
The HLFB is a serial connection. One wire from the first servo is connected to another wire of the next servo. The two ends of the chain is connected to the BoB 5V and an input.
The input from HLFB can then be used for various displays like actual speed/load of servos or for triggering a function.
What I am trying to achieve is that all servos stop if one servo stalls.
Here is the wiring:
Here is the engineer's explanation: