Apologies. This particular thread of conversation started with questions around signal integrity (pulse widths, and the like). That lead into a general concern if the breakout board (bob) might suffer in its design with the use of slow opto-isolators - devices that act like electronic switches, that would couple the stepper pulse from the computer to the stepper drivers. It’s a weakness in design that crops up from time to time and exhibits the problems you have witnessed. My post was simply to identify that these devices are not present on your bob, for the stepper driver signals, and that we shouldn’t get distracted with talks of changing bobs on the basis of an invalid assumption.