Yeah.. Mine was the same.. My shift registers were connected to these relay boards:
And, I also had a disconnect for the output side.. (I was using a 9v battery for launch, and had a switch)…
it makes no sense, but SOMEHOW, the problem I had was ONLY becoming an issue when the 9v was connected…
I’m sure I had a bad connection somewhere, but it will definitely be easier to find if I simplify..