Yup that's definitely the case. Not sure what I was doing wrong before, maybe cable quality.
Thanks for the input!
My initial question that got me into all this remains unanswered. It would be interesting to learn if the CAN bus can be a bottleneck as a hypothetical machine gets more and more motors on expansion/tool boards. There's finite bandwidth, how much machine is too much? Does the microstepping factor and/or feedrate affect bandwidth utilization? I may ask this as a question if I cannot figure it out myself